Musannaf Ibn Abi Shayba 19:936

Abu Bakr narrated to us, he said: Abd al-Rahim ibn Sulayman narrated to us, from Abd al-Malik ibn Sa’id ibn Hayyan, from Ammar al-Duhni, he said: Abu al-Tufayl narrated to me, he said: I was in the army that Ali ibn Abi Talib sent to the Banu Najiyah. He said: We reached them and found them in three groups. He said: Our commander said to one group of them: "Who are you?" They said: "We are a people from the Christians; we did not see a religion better than our religion, so we remained upon it." He said: "Withdraw." Then he said to another group: "Who are you?" They said: "We are a people who were Christians, then we accepted Islam, so we remained upon Islam." He said: "Withdraw." Then he said to the third: "Who are you?" They said: "We are a people who were Christians, then we accepted Islam, then we returned, and we did not see a religion better than our first religion, so we became Christians." He said to them: "Accept Islam," but they refused. He said to his companions: "When I wipe my head three times, then attack them." They did so, and they killed the combatants and took the offspring captive.