Musannaf Ibn Abi Shayba 13:2196

Abu Bakr narrated to us, he said: Muhammad bin Bakr narrated to us, from Ibn Jurayj, from ‘Ata’, he said: I said to him: A man made a *kitabah* (contract of manumission) with a slave of his, or he made a settlement with him, and he (the slave) concealed from him wealth of his—whether it was a slave, or gold/silver, or wealth other than that. He said: It belongs to the slave. And ‘Amr bin Dinar and Sulayman bin Musa said the same.