I kno
I know hadith are contested, I also know there are "quran only" Muslims, Shia too but here's a well known hadith.
Narrated 'Ikrima: Some
Zanadiqa (atheists) were brought to 'Ali and he burnt them. The news of this event, reached Ibn 'Abbas who said, "If I had been in his place, I would not have burnt them, as Allah's Apostle forbade it, saying, 'Do not punish anybody with Allah's punishment (fire).' I would have killed them according to the statement of Allah's Apostle, 'Whoever changed his Islamic religion, then kill him.'"
Sahih Bukhari 9:84:57