Musannaf Ibn Abi Shayba 13:2701

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Mubarak narrated to us, from al-Hasan, he said: Whoever was among them and then accepted Islam, he is free. And whatever they purchased from the captives of the Muslims and then he accepted Islam, he is to be sold among the Muslims.