Musannaf Ibn Abi Shayba 13:1585

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Abu Ja’far, from Ja’far ibn Abi Tharthawan, that Ali urged the people regarding Ibn al-Tayyah, so they collected for him more than his *mukātabah* (contract of manumission). A surplus remained, so Ali placed it among the *mukātabīn* (those in contracts of manumission).