There are numerous reports from non-Israeli sources that Yahya Sinwar was treated for a brain tumor in a hospital in Israel sometime between 2003 and 2008 (accounts differ on exact date and exactly where in Israel).
According to the Associated Press (2024),
"In 2008, Sinwar survived an aggressive form of brain cancer after
treatment at a Tel Aviv hospital."
The following are more detailed and seem more accurate. According to Reuters (Dec 2023),
"Bitton, a dentist who treated Sinwar, said Israeli medics removed a
tumour in Sinwar's brain in 2004."
The dentist, Yuval Bitton, was Jewish and diagnosed Sinwar's condition but did not provide in-hospital treatment. The Wall Street Journal reported (Dec 2023) that
"in 2004, Sinwar appeared to develop neurological problems, speaking
unclearly and struggling with walking, Bitton said. Doctors examined
him, finding an abscess in the brain that threatened his life. They
rushed him from a prison near Beer Sheva to the city’s hospital for
surgery. After a successful operation, Sinwar returned to prison and
thanked the doctors for saving his life..."
The last part is important for this question. Sinwar thanked the doctors in Hebrew. While in prison, he learned Hebrew in classes with the prison’s “open university” and read Israeli newspapers. Via the Manhattan Institute (Mar 2024),
The Palestinian in the clinic at one of Israel’s highest security
prisons near Beersheba had a persistent pain in the back of his neck.
He trembled and had trouble walking. Yuval Bitton, then a 28-year-old
dentist just a year out of school, suspected that his patient might be
suffering from a C.V.A., an ischemic cerebrovascular accident,
resulting from a life-threatening brain tumor. “He needs to be
hospitalized, immediately,” Bitton advised the prison doctors.
Dr. Bitton’s diagnosis was quickly confirmed at the Soroka Medical
Center in Beersheba. The surgery took hours. The prisoner survived...
he thanked Bitton and the rest of the
prison medical staff for having saved his life—in excellent Hebrew.
The year was 2004. The patient was Yahya Sinwar.
There are Arab Israelis, some of whom are Muslim. They speak Hebrew, but it seems unlikely that Sinwar would thank an Arab Muslim physician in Hebrew.
There is an additional source that further corroborates that Yahya Sinwar was treated by Jewish physicians. Hussain Abdul-Hussain is the Washington bureau chief of Kuwaiti daily Al-Rai. Before that, he managed the Iraqi stream of the Arabic TV network Alhurra. He worked as a reporter and editor in Beirut for Lebanon’s The Daily Star. On 2 January 2024, he made the following response on Twitter to Saira Rao (who expressed terror and fear for the well-being of "Palestinian, Arab, Muslim, South Asian and Black patients" in the U.S. because "many American doctors and nurses are Zionists")
Just like how Zionist Israeli doctors saved the life of top Hamas
leader Yahya Sinwar when he was in Israeli prison and a tumor was
found in his head? Israel has made most Arabs think that Palestinians
are lucky to have ethical Israelis as their enemy, especially when
compared to #Iran regime...
The relevant part is Abdul-Hussain's description of the doctors who saved the life of Sinwar: "Zionist Israeli doctors". The combination of speaking Hebrew and the description of them as Zionist Israelis makes it very likely that they were Jewish.
An article via Bloomberg confirms (Nov 2023) part of what the other answer here described:
Betty Lahat, the prison system’s intelligence chief at the time, said
she tried to use that event to recruit him as
an agent. “I said, the state of Israel saved your life... I
thought I could turn him into one of ours, but he wasn’t
interested...”