Musannaf Ibn Abi Shayba 13:1126

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Isra’il, from Jabir, from ‘Amir, regarding a man who enters into a contract of manumission (kitabah) for his share of a slave: He said: If his partners know [of it] before he pays [the amount], he may revoke it. But if he has paid, he may not revoke it.