Musannaf Ibn Abi Shayba 13:2136

Abu Bakr narrated to us, he said: Yahya ibn Adam narrated to us, he said: Isra'il narrated to us, from Mughirah, from Ibrahim, regarding a man who pledged a slave then emancipated him. He said: The emancipation of the slave is valid, and the pledgee shall pursue the pledger [for the value of the slave].