Is "X" kufr (reference question)

Question

Kufr is often defined as disbelief; to what extent does this simple definition cover the meaning of Kufr in Islam?

Motivation: We have a load of questions (see the hopefully growing list at the end) on the site where someone is in doubt ofhaving committed an act which can be regarded as kufr and asks whether Allah will forgive him or her. I think that all of these questions essentially have the same answer and it is counterproductive to repeat it all the time. The act of kufr itself and the backstory of the one asking the question is largely irrelevant.
I'd like to cover as many aspects of Kufr as possible starting with a useful definition. And to as completely as possible, cover the topic of Kufr, in order to use this as a reference question.

So please address in your answer the following question parts:

• What is the definition of the term Kufr?
• What constitutes Kufr (which acts and preconditions are necessary)?
• Can Kufr be forgiven and is the process of repentance different than that of repenting from a sin?
• What are the conditions for it (possibly) being forgiven?
• What if such an act was made unintentionally or without knowing it was kufr?

As the question is intended as a reference question, the answer should include evidence and have at least canonical level.

Some examples of former questions:

• Did I commit kufr?
• Doing black magic but you did not know shirk was a sin
  (feel free to expand the list even with posts including answers)

Answer 1

< work in process >

Definition:

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Kufr is the denial of anything which is known by to be a part of the religion of Islam, i.e. the shariah of Muhammad ﷺ, through ijma or tawatur.

See e.g. al-Manthoor fi’l-Qawaa’id al-Fiqhiyyah.

Acts which constitute Kufr:

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Kufr occurs by any belief, speech or act which implies denial of any part of Islam as stated above.

It is impractical to compile a complete list of all things which constitute Kufr. Some of the major ones which are recorded by the scholars include:

• Denial of the existence of Allah
• Believing that Allah has partners or children.
• Denial of any of the attributes of Allah.
• Abusing or mocking Allah and the angels
• Prostration to an idol or the sun or moon.
• Denial of the existence of the prophets or of revelation.
• Belying any of the prophets
• Believing that Muhammad was only meant for the Arabs, or that there can be or has been a prophet after him.
• Abusing or mocking any of the prophets
• Believing the world to have existed from forever, or believing that it will exist forever.
• Believing in reincarnation of souls,
• Denial of heaven and hell and reward and punishment
• Denial of any verse or word of the Quran
• Considering something which is halal to be haram, such as marriage or trade.
• Considering something which is haram to be halal, such as adultery or wine.
• Considering something which is obligatory to be voluntary, such as the five daily prayers.
• Considering something which is voluntary to be obligatory, such as the fasts of Shawal.
• Desecrating the Quran, e.g. by throwing it into filth.
• Not Considering religions other than Islam, such as Christianity and Judaism to be Kufr. Or having a doubt about their disbelief.
• Denying the miracle of the Quran or claiming the ability to produce something like it
• Considering sihr to be permissible
• Having the intention to commit Kufr in future
• Considering all of the sahaba to be disbelievers, or denying the companionship of Abu Bakr, or the chastity of Aisha.

Some matters which are disputed include:

• abandoning salah
• calling another Muslim a disbeliever
• practicing or learning sihr
• abusing (some of) the sahaba

Reference: Mughni al-Muhtaaj Volume 5 Page 428-432 and Kashshaaf al-Qinaa’ Volume 6 Page 168-188 and Mawaahib al-Jaleel Volume 6 Page 485-491 and Bahr ar-Raa’iq Volume 5 Page 202-210.

Conditions in which Kufr is invalid:

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An act of Kufr by a Muslim will not be valid if done under the following states:

• Infancy
• Insanity
• Coercion
• Anything uttered by a slip of the tongue

A young child or insane person lacks proper judgement and so are exempt in the hadith about the three kinds of people from whom the pen is lifted (Abu Dawud 4403). When Kufr is done under coercion it is excused because of the Quranic verse (Quran 16:106). Slips of the tongue are excused as is implied by the hadith about the person who mistakenly called Allah his slave (Muslim 2747) . That such unintentional mistakes and coercion are excused is also proven by the hadith which says that they are forgiven (Ibn Majah 2045).

Conditions regarding which there is disagreement:

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There is difference of opinion on whether Kufr done in the following states is valid:

• Ignorance. Meaning a statement or belief by a Muslim who has done the act intentionally but was unaware that it amounted to Kufr and he did not mean to do Kufr. This may happen because of being new to Islam or living away from Muslims and scholars.

• Drunkenness. Meaning a statement or act done by a Muslim who willingly consumed an intoxicant (like wine) and under its influence did something which amounted to Kufr.

Some of the scholars hold that these are not admissible excuses and Kufr done in these states will nullify a person's Islam. However some hold that they are valid excuses since intention was not present.

In either case one should be cautious and should correct himself and should seek forgiveness from Allah.

Reference: For 'ignorance' see Ghamz ‘Uyoon al-Basaa’ir, Volume 3 Page 304. These conditions are also discussed in the above linked texts which enumerate the acts constituting Kufr.

Conditions which do not excuse an act of Kufr:

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A person who does kufr in anger or jest has done Kufr in reality. Quran 9:65-66.

Forgiveness from Kufr:

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This depends on whether the person sincerely repents and accepts Islam before his death. Allah has stated that in the absence of repentance He will not forgive Kufr. See 9:80 , 3:91, 2:217 etc.

However after repentance Kufr can be forgiven:

قل للذين كفروا إن ينتهوا يغفر لهم ما قد سلف

Say to those who have disbelieved [that] if they cease, what has previously occurred will be forgiven for them.

^{— Quran 8:38}

إلا الذين تابوا من بعد ذلك وأصلحوا فإن الله غفور رحيم

Except for those who repent after that [i.e. apostasy] and correct themselves. For indeed, Allah is Forgiving and Merciful.

^{— Quran 3:89}

Repentance from Kufr includes repeating the Shahada and declaration of disassociation from the false belief or deed which caused Kufr. For further details on the process of repentance see Does the process of repentance differ significantly based on the sin?.

Answer 2

Asalaam Alaikum

DEFINITIONS OF KUFR

• IN ARABIC USAGE

the term kufr comes from the arabic verb kafara, which means to cover up, conceal or deny. this is the same as to cover, hide, and disbelieve. the three-letter root of both of these words, bears meanings that range from covering and hiding to disbelief, ingratitude, infidelity and godlessness. (Al-Ba‟albaki, 1995)

• ACCORDING TO QURAN

kufr means to disagree, to reject or not to give declaration to any one of the commands and prohibitions bestowed by Allah (SWT) and shown by Muhammad (P.B.U.H). the term kufr and shirk can be interchangeable. shirk could refer to associating others in worship to Allah, and kufr could refer to what is greater than that to include shirk and disbelieving in one of the pillars of islam, or other acts in the heart. if these two terms are mentioned in one context, their meaning is different, but if only one term is mentioned, then it includes the meaning of the other one.

SOME DEFINITIONS OF KUFR BY SCHOLARS

• Shaykh al-Islam Ibn Taymiyah (rahimahullaah)

not believing in Allah and His messenger, whether that is accompanied by denial or it is not accompanied by denial but rather doubt, or turning away from faith out of jealousy or arrogance, or because one is following whims and desires that prevent one from following the message. so kufr is the attribute of everyone who rejects something that Allah has commanded us to believe in, after news of that has reached him, whether he rejects it in his heart without uttering it, or he speaks those words of rejection without believing it in his heart, or he does both; or he does an action which is described in the texts as putting one beyond the pale of faith. [ Majmoo’ al-Fataawa by Shaykh al-Islam Ibn Taymiyah, 12/335; al-Ihkaam fi Usool al-Ahkaam by Ibn Hazam, 1/45 ]

• Imam Ibn Baz (rahimahullaah)

Kufr is the denial and concealment of the Truth such as those who deny the obligation of Salah, Zakah, Sawm, Hajj in case of being financially and physically able, and dutifulness to one’s parents, and so on. It is also like those who deny the prohibition of Zina (premarital sexual intercourse and/or adultery), consuming Khamr (intoxicants), and disobeying one’s parents. [ Majmoo’ al-Fataawa vol.09]

• Ibn Hazam (rahimahullaah)

Rejecting something for which there is sound proof that there can be no faith without believing in it is kufr, and uttering words for which there is proof that uttering them is kufr is kufr. Doing any action for which there is proof that it is kufr is also kufr. [ al-Fasl ]

• Imam Nawawi (rahimahullaah) in his commentary of sahih muslim it is mentioned regarding the following hadith ;

It is narrated on the authority of Abu Zubair that he heard Jabir b. 'Abdullah saying. I heard the Messenger of Allah (may peace and blessings be upon him) observing this: Between man and polytheism and unbelief is the abandonment of salat. [Sahih Muslim 82b]

He said: "Shirk and Kufr could be mentioned to mean one thing, which is disbelief in Allaah. But their meaning could differ, Shirk could mean worshipping idols or other creatures while acknowledging the existence of Allaah, like the Kufar of Quraysh, so the term Kufr is more general than Shirk."

TYPES OF KUFR

In Islam, it is believed that kufr may arise in a variety of forms of which all faithful Muslims must be wary. disbelief may arise from stubbornness to admit the truth, from pride and arrogance, from ingratitude towards Allah, from disobedience or unwillingness to comply with any one of the principles of Islam, from mockery of Allah's prophets, signs or teachings or from the hypocrisy by those professing to believe while concealing unbelief.

• Ibn Al-Qayyim has classified kufr as ;

1. kufr taktheeb (disbelief due to rejection)

this is to believe that the messengers of Allah the mighty and sublime are not truthful. to believe that they have not delivered the message to us fully. rejecting the message fully or parts of it. rejection happens when a person knows the truth but still denies it. similar to this is the kufr of permitting that which is forbidden. whoever regards as permissible something which he knows that Islam has forbidden has disbelieved in the messenger (P.B.U.H) and in that which he brought. the same applies to one who forbids something which he knows that Islam has permitted. [ see (2:89), (2:146), (27:14) and (6:33) ]

2. Kufr Istikbaar (disbelief due to arrogance and pride whilst one acknowledges the truth)

it is like the Kufr of Iblees (Satan), for he did not deny the command of Allah, and he did not face it with rejection, but he responded to it with arrogance and pride. from this comes the disbelief of the one who knows the truthfulness of the messenger and that he has come with the truth from Allah but does not comply with it due to arrogance and pride. [ see (2:34), (23:47), (91:11) and (14:10) ]

3. Kufr I’raadh (disbelief due to turning away/ignoring)

it is to turn away with one’s hearing and one’s heart from the Messenger, neither believing in him nor rejecting him, neither allying with him nor showing enmity towards him, and not paying attention to that which he came with at all.

4. Kufr Shakk (disbelief due to doubt)

it is when one is not certain of the Messenger’s truthfulness and one does not disbelieve in him but has doubts about him.

5. Kufr Nifaaq (disbelief due to hypocrisy)

it is when a person shows belief with his tongue while rejection is hidden in his heart. this takes the form of not believing in the heart and not acting, whilst submitting outwardly in order to show off to people.

we must understand that not all acts of kufr takes the person out of the fold of islam. unintentional thoughts (waswaas) are not to be considered as something that would keep the person out of the lines of islam, as long as we don't harbor those thoughts and cultivate them into actions. this claim is proven with the following evidence from sunnah,

Narrated 'Umar bin Al-Khattab:I heard Allah's Messenger (ﷺ) saying, "The reward of deeds depends upon the intentions and every person will get the reward according to what he has intended. [bukhari(1)]

and

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said, "Verily, Allah has pardoned my nation for what occurs within themselves, as long as they do not speak of it or act upon it". [bukhari(5269) and muslim(127)]

further this is clarified in ;

narrated from Ibn ‘Abbaas (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said, relating from his Lord, may He be glorified and exalted: "Allah decreed good deeds and bad deeds, then He explained that. Whoever thinks of doing a good deed then does not do it, Allah will write it down as one complete good deed. If he thinks of doing a good deed and then does it, Allah [may He be glorified and exalted] will write it down between ten and seven hundred fold, or many more. If he thinks of doing a bad deed then he does not do it, Allah will write it down as one complete good deed, and if he thinks of it then does it, Allah will write it down as one bad deed." [bukhari(6491) and muslim(131)]

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now that we have an understanding of kufr, i believe it is worthy to remind ourselves of what things that would take us out of the fold of islam. things that would nullify our islam. various scholars have mentioned numerous things that can take a person out of the fold of islam. Shaykh al-Islam Muhammad Ibn Abdil Wahhab has listed 10 things that would nullify our islam. these are the most obvious and the most important things according to the sheikh.

THINGS THAT NULLIFY ONE'S ISLAM

The things that nullify one's Islaam (nawaaqidh) are ten. Nawaaqidh is the plural of naaqidhah, and they are things that render something ineffective, like the nawaaqidh that nullify one's wudhoo', for example, are the things that render the wudhoo' null and void.

1.shirk in one's worship of Allah.

Verily Allaah does not forgive that partners be ascribed to Him, while He forgives what is less than that for whomever He wants.(4:116) and He, the Most High, has said Verily whoever ascribes a partner to Allah, then Allah has made Paradise haraam (impermissible) for him (i.e. He will never enter it), and his abode is the Fire. And there are no helpers for the oppressors whatsoever.(5:72)

2. Whoever sets up intermediaries between himself and Allah, calls on them, asks them for things, and places his trust in them, then he has disbelieved, by way of scholarly consensus.

3. Whoever does not declare the poly theists to be disbelievers, or he doubts their disbelief or approves of their way, then he has disbelieved.

4. Whoever believes that guidance other than Muhammad's (may Allah raise his rank and grant him peace) is more complete than his, or that the rulings of others are better than his rulings, like the one who prefers the rulings of at-tawaagheet over his rulings, then he is a disbeliever.

5. Whoever hates something that the Messenger (may Allah raise his rank and grant him peace) came with, even if he acts according to it, then he has disbelieved.

6. Whoever mocks anything from the Religion of the Messenger or Allah's reward or punishment has disbelieved.

The proof is the statement of Allah the Most High: "Say: 'Was it Allah, His Verses, or His Messenger you were mocking? Make no excuse, verily you have disbelieved after your belief.(9:65-66)

7. Magic, like as-sarf and al- ' atf, whoever practices it or is pleased with it, has disbelieved.

The proof is His Statement: "And they (the two who taught magic) did not teach anyone before first saying, 'We are merely a tribulation, so do not disbelieve. (2:102)

8. Trying to give the polytheists victory and assisting them against the Muslims.

And the proof is His Statement: "And whoever of you takes them (the Jews and Christians) as allies, then he is from them. verily Allah does not guide the oppressive people.(5:51)

9. Whoever believes that some people are allowed to go against the Sharee 'ah of Muhammad (may Allah raise his rank and grant him peace), like how al-Khadhir went against the Sharee'ah of Moosaa, peace be upon him, then he is a disbeliever.

10. turning away from the Religion of Allah, not learning it and not acting by it.

And the evidence is His Statement, "And who is more oppressive than the one who is reminded with the Verses of his Lord and then he turns away from them? Verily, We will get retribution from the criminals.(32:22)

with this much said, i will mention a couple of questions answered by Shaykh al-Islam Muhammad Ibn Abdil Wahhab, which i believe is relevant to the context of this matter which we have discussed.

• [Ql3] : Is the one who is ignorant of these things that nullify one's Islaam to be excused?

• [Al3] : Ignorance is of different types. If it is not possible for the ignorant person to learn, then he is to be excused until he finds someone to teach him, like the one who lives in a land far away from the lands of the Muslims, and only disbelievers live there. Such a person is to be excused on account of his ignorance. But as for the one who lives amongst the Muslims in the lands of the Muslims, hearing the Quran and hearing the ahaadeeth, hearing the speech of the people of knowledge, then such a person is not to be excused on account of ignorance, since the proof has reached him and he has not concerned himself with it.

• [Q14]: If someone has committed one of these acts that nullify one's Islam and then repented, is this repentance valid?

• [A14]: Yes, if he repents, then Allah will accept his repentance. Allah accepts the repentance of all sinners, those who apostate and other than them. if a person dies as a repenting Muslim, then Allah accepts his repentance, as Allah accepts the repentance of the apostate and anyone else who repents to Allah, the Mighty and Majestic.

just to have a more clearer and an easier understanding, let us look at the 4 pillars of kufr identified by Imam Ibn Qayyim,

• haughtiness and disdainfulness : this prevents the person from submission before Allah the mighty and sublime.

• envy (al hasad) : this prevents the person from accepting naseehah.

• anger (al ghadab) : this prevents the person from being just.

• lusts : this prevents the person from giving himself to worship of Allah.

If the pillar of false pride and haughtiness is demolished, then submission will become easy for him. If the pillar of envy is demolished, then it becomes easier for him to accept advice and to offer it. If the pillar of anger is demolished, it becomes easy for him to be just and humble. If the pillar of lust is demolished, it becomes easy for him to be patient and ready for worship.

The origin of these four pillars is from man’s ignorance concerning his Lord and ignorance concerning himself. Had he known of his Lord qualified with the most perfect and magnificent attributes and had he known himself qualified with all forms of defects, he wouldn’t be haughty, angry, envious of others because envy in fact is one form of opposition to Allah because he dislikes the favor and blessing of Allah which he bestowed upon his slave while Allah loves that.

this subject of kufr/shirk is very important and very vast as well. i believe with this effort a person can have a more clearer understanding about kufr and how to identify them at the very least, insha Allah.

whatever mistake or error their might be in the answer it is from me, may Allah rectify me

may Allah the mighty and sublime grant us mercy and guide us to the straight path.

ALLAH KNOWS BEST

Answer 3

Definition

In the Arabic language, Kufr is the denial of something. The latter can be in a form of 1) ingratitude, or 2) negation and non-belief of a claim or fact.

Examples from Quran:

• In Surat Al-Mumtahina, the word "Kafarna", which is the past tense of "Kufr" in plural form, means "Rejection" and "Denial" of someone's claims:

قَدْ كَانَتْ لَكُمْ أُسْوَةٌ حَسَنَةٌ فِي إِبْرَاهِيمَ وَالَّذِينَ مَعَهُ إِذْ قَالُوا لِقَوْمِهِمْ إِنَّا بُرَاء مِنكُمْ وَمِمَّا تَعْبُدُونَ مِن دُونِ اللَّهِ كَفَرْنَا بِكُمْ وَبَدَا بَيْنَنَا وَبَيْنَكُمُ الْعَدَاوَةُ وَالْبَغْضَاء أَبَداً حَتَّى تُؤْمِنُوا بِاللَّهِ وَحْدَهُ

There is for you an excellent example (to follow) in Abraham and those with him, when they said to their people: "We are clear of you and of whatever ye worship besides Allah: we have rejected you, and there has arisen, between us and you, enmity and hatred for ever,- unless ye believe in Allah and Him alone".

• In Surat An-Nahl, the word fa "kafarat", which is the past tense of Kufr in feminine form, means "the denial of the grace and favor".

وَضَرَبَ اللّهُ مَثَلاً قَرْيَةً كَانَتْ آمِنَةً مُّطْمَئِنَّةً يَأْتِيهَا رِزْقُهَا رَغَداً مِّن كُلِّ مَكَانٍ فَكَفَرَتْ بِأَنْعُمِ اللّهِ فَأَذَاقَهَا اللّهُ لِبَاسَ الْجُوعِ وَالْخَوْفِ بِمَا كَانُواْ يَصْنَعُونَ

And Allah sets forth a parable: (Consider) a town safe and secure to which its means of subsistence come in abundance from every quarter; but it became ungrateful to Allah's favors, therefore Allah made it to taste the utmost degree of hunger and fear because of what they wrought.

Similarly, in the Islamic terminology, Kufr is the denial and rejection of:

• either 1) the existence of Allah. For example, in Surat Al-Kahf, the word "Akafarta", which translates to "Did you do Kufr", means "the denial of ِthe existence of Allah":

قَالَ لَهُ صَاحِبُهُ وَهُوَ يُحَاوِرُهُ أَكَفَرْتَ بِالَّذِي خَلَقَكَ مِن تُرَابٍ ثُمَّ مِن نُّطْفَةٍ ثُمَّ سَوَّاكَ رَجُلاً

His companion said to him, in the course of the argument with him: "Dost thou deny Him Who created thee out of dust, then out of a sperm-drop, then fashioned thee into a man?

• or 2) the oneness of God (i.e. Monotheism): in Surat Al-Maeda, Allah explicitly stated that non-Monotheism is Kufr:

لَّقَدْ كَفَرَ الَّذِينَ قَالُواْ إِنَّ اللّهَ ثَالِثُ ثَلاَثَةٍ وَمَا مِنْ إِلَـهٍ إِلاَّ إِلَـهٌ وَاحِدٌ وَإِن لَّمْ يَنتَهُواْ عَمَّا يَقُولُونَ لَيَمَسَّنَّ الَّذِينَ كَفَرُواْ مِنْهُمْ عَذَابٌ أَلِيمٌ

Certainly they disbelieve who say: Surely Allah is the third (person) of the three; and there is no god but the one Allah, and if they desist not from what they say, a painful chastisement shall befall those among them who disbelieve.

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Types of Kufr

In Islam, there are two types of Kufr, small and big. The latter is the one that makes the person who conducts it, totally non-Muslim, whereas the former does not, yet it is risky.

1. Example of small Kufr is wailing on deceased person out loud: it's mentioned in Sahih Muslim that the messenger of Allah (PBUH) said:

اثنتان في الناس هما بهم كفر الطعن في النسب، والنياحة على الميت

Two matters are signs of disbelief on the part of those who indulge in them: Defaming a person's lineage and wailing over the dead.

2. Example of big Kufr is swearing Allah, the religion or prophet Muhammad (PBUH). Also deeming permissible what is Haram and vice versa as the latter directly rejects and denies the Sharia of Islam:

In Surat An-Nahl, Allah said:

وَلَا تَقُولُوا لِمَا تَصِفُ أَلْسِنَتُكُمُ الْكَذِبَ هَٰذَا حَلَالٌ وَهَٰذَا حَرَامٌ لِتَفْتَرُوا عَلَى اللَّهِ الْكَذِبَ ۚ إِنَّ الَّذِينَ يَفْتَرُونَ عَلَى اللَّهِ الْكَذِبَ لَا يُفْلِحُونَ

And do not say because of the lies which your tongues utter, `This is lawful and that is unlawful,' lest you should forge a lie against Allah. Those who forge lies against Allah will never attain the goal.

Imam Ishaq ibn Rahwayh said in As-Sarim al-Maslul book:

It is agreed unanimously by all scholars that whoever swears Allah (SWT) or his Messenger (PBUH) ...... even if he/she believes in Allah, he/she is Kafir"

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Main Acts of Kufr

There are 10 agreed-on acts that make a person a big kafir, they are:

1. Doing Shirk (i.e. associating partner(s) with Allah), including calling on deceased people for help, and Qurbani (i.e. slaughter an animal) to anyone other than Allah. Allah said in Surat An Nisa:

إِنَّ اللَّهَ لَا يَغْفِرُ أَنْ يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَنْ يَشَاءُ ۚ وَمَنْ يُشْرِكْ بِاللَّهِ فَقَدْ ضَلَّ ضَلَالًا بَعِيدًا

Verily! Allah forgives not (the sin of) setting up partners in worship with Him, but He forgives whom he pleases sins other than that, and whoever sets up partners in worship with Allah, has indeed strayed far away.

2. Considering anyone beside Allah as a "mean" between the person and Allah. Allah said in Surat Yunus:

وَيَعْبُدُونَ مِنْ دُونِ اللَّهِ مَا لَا يَضُرُّهُمْ وَلَا يَنْفَعُهُمْ وَيَقُولُونَ هَٰؤُلَاءِ شُفَعَاؤُنَا عِنْدَ اللَّهِ ۚ قُلْ أَتُنَبِّئُونَ اللَّهَ بِمَا لَا يَعْلَمُ فِي السَّمَاوَاتِ وَلَا فِي الْأَرْضِ ۚ سُبْحَانَهُ وَتَعَالَىٰ عَمَّا يُشْرِكُونَ

And they worship other than Allah that which neither harms them nor benefits them, and they say, "These are our intercessors with Allah " Say, "Do you inform Allah of something He does not know in the heavens or on the earth?" Exalted is He and high above what they associate with Him

3. Calling or Considering non-Muslims as non-Kafir. That is because this act rejects and denies the explicit verses in Quran which state that anyone comes in the Judgment day as non-Muslim, he/she will reside in hellfire.

Allah said in Surat Aal Omran:

وَمَنْ يَبْتَغِ غَيْرَ الْإِسْلَامِ دِينًا فَلَنْ يُقْبَلَ مِنْهُ وَهُوَ فِي الْآخِرَةِ مِنَ الْخَاسِرِينَ

And whoever desires other than Islam as religion - never will it be accepted from him, and he, in the Hereafter, will be among the losers.

Hadith in Sahih Muslim: It is narrated on the authority of Abu Huraira that the Messenger of Allah (may peace be upon him) observed: By Him in Whose hand is the life of Muhammad, he who amongst the community of Jews or Christians hears about me, but does not affirm his belief in that with which I have been sent and dies in this state (of disbelief), he shall be but one of the denizens of Hell-Fire.

4. Believing that the Sharia Law and Guidance of prophet Muhammad (PBUH) are incomplete/ imperfect, so people should remove from or add to them. For example: believing that secular or humans' laws are better than Sharia Law. Allah said in Surat Almaida (note that this verse strictly is about the belief that Sharia Law is imperfect, unlike the Kharijites who consider even the person who does not "practice" some Sharia laws as Kafir):

وَمَنْ لَمْ يَحْكُمْ بِمَا أَنْزَلَ اللَّهُ فَأُولَٰئِكَ هُمُ الْكَافِرُونَ

And he who does not judge according to that (law) which Allah has revealed, it is these who are the real disbelievers.

5. Loathing (in a form of denying) anything in the message of prophet Muhammad (PBUH). Allah said in Surat Muhammad:

ذَلِكَ بِأَنَّهُمْ كَرِهُوا مَا أَنْزَلَ اللَّهُ فَأَحْبَطَ أَعْمَالَهُمْ

That is because they hate the Revelation of Allah; so He has made their deeds fruitless

6. Mocking anything in the Islamic religion. Allah said in Surat Attawaba:

وَلَئِنْ سَأَلْتَهُمْ لَيَقُولُنَّ إِنَّمَا كُنَّا نَخُوضُ وَنَلْعَبُ ۚ قُلْ أَبِاللَّهِ وَآيَاتِهِ وَرَسُولِهِ كُنْتُمْ تَسْتَهْزِئُونَ لَا تَعْتَذِرُوا قَدْ كَفَرْتُمْ بَعْدَ إِيمَانِكُمْ

And if you should question them, they would certainly say: We were only idly discoursing and sporting. Say: Was it at Allah and His communications and His Apostle that you mocked? Do not make excuses. You have disbelieved after you believed.

7. Practicing Sorcery & Magic (this act most of scholars agree on). Allah said in Surat Al Baqarah:

وَاتَّبَعُوا مَا تَتْلُو الشَّيَاطِينُ عَلَىٰ مُلْكِ سُلَيْمَانَ ۖ وَمَا كَفَرَ سُلَيْمَانُ وَلَٰكِنَّ الشَّيَاطِينَ كَفَرُوا يُعَلِّمُونَ النَّاسَ السِّحْرَ وَمَا أُنْزِلَ عَلَى الْمَلَكَيْنِ بِبَابِلَ هَارُوتَ وَمَارُوتَ ۚ وَمَا يُعَلِّمَانِ مِنْ أَحَدٍ حَتَّىٰ يَقُولَا إِنَّمَا نَحْنُ فِتْنَةٌ فَلَا تَكْفُرْ

And they followed [instead] what the devils had recited during the reign of Solomon. It was not Solomon who disbelieved, but the devils disbelieved, teaching people magic and that which was revealed to the two angels at Babylon, Harut and Marut. But the two angels do not teach anyone unless they say, "We are a trial, so do not disbelieve [by practicing magic]".

8. Helping non-Muslims against Muslims and being loyal to them over Muslims (pay attention to the context here, because helping non-Muslims in general is permissible as per stated in Quran). Allah said in Surat Almaidah (here the word "friends" come in the meaning of "allies" over Muslims) and in Surat Al-Emran, respectively:

يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَتَّخِذُوا الْيَهُودَ وَالنَّصَارَىٰ أَوْلِيَاءَ ۘ بَعْضُهُمْ أَوْلِيَاءُ بَعْضٍ ۚ وَمَنْ يَتَوَلَّهُمْ مِنْكُمْ فَإِنَّهُ مِنْهُمْ

O ye who believe! take not the Jews and the Christians for your friends and protectors: They are but friends and protectors to each other. And he amongst you that turns to them (for friendship) is of them.

لَا يَتَّخِذِ الْمُؤْمِنُونَ الْكَافِرِينَ أَوْلِيَاءَ مِنْ دُونِ الْمُؤْمِنِينَ وَمَنْ يَفْعَلْ ذَلِكَ فَلَيْسَ مِنَ اللَّهِ فِي شَيْءٍ إِلَّا أَنْ تَتَّقُوا مِنْهُمْ تُقَاةً وَيُحَذِّرُكُمُ اللَّهُ نَفْسَهُ وَإِلَى اللَّهِ الْمَصِيرُ

Let not believers take disbelievers as allies rather than believers. And whoever [of you] does that has nothing with Allah, except when taking precaution against them in prudence. And Allah warns you of Himself, and to Allah is the [final] destination.

9. Justifying religions other than Islam and believing that other religions grant you paradise in the afterlife. Proof from Quran and Hadith is similar to point 3 above. Ibn Taymiyyah in Al Fatawa Al Kubra book said:

It is known be necessity, and agreed by all Muslims, that justifying a religion other than the religion of Islam or following Sharia other than Sharia prophet Muhammad (PBUH) came with, is Kufr.

10. Aversion to and disregard of the Islamic religion, where the person does not learn it, nor he/she practices it, so they completely turn away from it, in which the person neither believe nor disbelieve prophet Muhammad (PBUH). Allah said in Surat Assajdah:

وَمَنْ أَظْلَمُ مِمَّن ذُكِّرَ بِـَٔايَٰتِ رَبِّهِۦ ثُمَّ أَعْرَضَ عَنْهَآ ۚ إِنَّا مِنَ ٱلْمُجْرِمِينَ مُنتَقِمُونَ

And who is more unjust than he who is reminded of the communications of his Lord, then he turns away from them? Surely We will give punishment to the guilty.

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Repentance

Regarding the repentance from big Kufr: A person who committed any big Kufr, should:

1. Do Shahada again;
2. Have remorse;
3. Intend and determine to never do this Kufr again;
4. Repent to Allah;
5. Start doing good deeds.