Musannaf Ibn Abi Shayba 13:1782

Abu Bakr narrated to us, he said: Yahya ibn Adam narrated to us, from Zuhayr, from Mughirah, from Ibrahim and al-Sha’bi regarding a slave who is between two men, and one of them emancipates his share. They both said: He is emancipated from the wealth of the one who emancipated him, and he shall guarantee to his partner [the value of his share] according to a fair valuation on the day he emancipated him.