Musannaf Ibn Abi Shaybah

Hazrat Ikrimah (may Allah have mercy on him) narrates that Hazrat Ibn Abbas (may Allah be pleased with them both) mentioned those people whom Hazrat Ali (may Allah be pleased with him) had burnt, then said: If I had been there, I would never have burnt those people, because of the saying of the Messenger of Allah (peace and blessings be upon him): "Do not punish with the punishment of Allah." And if I had been there, I would have killed them, because of the noble saying of the Messenger of Allah (peace and blessings be upon him): "Whoever changes his religion, kill him."