Musannaf Ibn Abi Shaybah 34948 — What they said on a man who accepts

Ubaydullah bin Utbah (may Allah have mercy on him) says: Some people of the tribe of Banu Hanifah who had been with Musaylimah the Liar used to spread his sayings openly and recite them. Sayyiduna Ibn Mas'ud (may Allah be pleased with him) seized them, then informed Sayyiduna Uthman (may Allah be pleased with him) about them by letter. Sayyiduna Uthman (may Allah be pleased with him) wrote back: "Invite these people to Islam. Whoever among them testifies that there is no god worthy of worship but Allah and that Muhammad (peace and blessings be upon him) is the Messenger of Allah, and abandons disbelief and chooses faith, accept that faith from them and let them go on their way. And if they refuse, strike their necks." So Sayyiduna Ibn Mas'ud (may Allah be pleased with him) asked them to repent. Some of them repented and some of them refused, so he (may Allah be pleased with him) struck the necks of those who refused.