Musannaf Ibn Abi Shayba 13:1898

Abu Bakr narrated to us, he said: Abd al-Salam narrated to us, from Yazid ibn Abd al-Rahman al-Dalani, from Ibrahim [al-Sa'igh], from Nafi', from Ibn Umar, regarding a slave between two people, where one of them emancipates his share. He said: It is upon him to emancipate the remainder of him. If he does not have [the means], the slave shall work to earn the remainder of his price, and they shall be partners in the wala' (patronage).