Musnad Ahmad 27:1578

Hashim narrated to us, Layth narrated to us, from Nafi’, from ‘Abdullah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whichever slave is between two partners, and one of them emancipates his share, then the value of the slave shall be appraised fairly from the wealth of the one who emancipated [his share]. If his wealth reaches that [amount], he [the slave] is emancipated."