Musannaf Ibn Abi Shaybah 34949 — What they said on the apostate: how

Abd al-Rahman (may Allah have mercy on him) says: When the news of the conquest of Tustar was brought to Sayyiduna Umar (may Allah be pleased with him) (Tustar is a region of Basra), he (may Allah be pleased with him) asked them: "What news is there from afar?" The people said: "There was a man from the Muslims who joined the polytheists. We seized him." He (may Allah be pleased with him) asked: "How did you deal with him?" They said: "We killed him." He (may Allah be pleased with him) said: "Why did you not put him in a house and shut the door on him, that is, imprison him, and give him a loaf of bread every day, then ask him to repent three times? Then if he repented, well and good; otherwise you would have killed him." Then he (may Allah be pleased with him) said: "O Allah, I was not a witness to them, nor did I order them, and when the news of this reached me, I was not pleased with it."