Musannaf Ibn Abi Shaybah 34930 — What they said on a man who accepts

Amir (may Allah have mercy on him) said that Sayyiduna Anas bin Malik (may Allah be pleased with him) said: A group from the tribe of Bakr bin Wa'il apostatized from Islam and joined the polytheists, and they were killed in the fighting. When I came to Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) with the news of the conquest of Tustar, he (may Allah be pleased with him) said: "What happened to the people of the tribe of Bakr bin Wa'il?" The narrator said: I began another topic before him (may Allah be pleased with him) to divert him (may Allah be pleased with him) from mentioning them, but he (may Allah be pleased with him) asked again: "What happened to the group from the tribe of Bakr bin Wa'il?" I said: "O Commander of the Faithful, they were killed." He (may Allah be pleased with him) said: "If I had taken them peacefully, that would have been dearer to me than all the gold and silver on which the sun rises." The narrator said: I said: "O Commander of the Faithful, if you (may Allah be pleased with him) had caught those people who apostatized from Islam and joined the polytheists, what way could there have been except killing them?" He (may Allah be pleased with him) said: "I would have put it to them to enter by the same door through which they had left. If they did so, I would have accepted this from them, and if they refused, I would have confined them in prison."