Sahih Bukhari: Hadith 2401

Ibn `Umar said, "Allah's Messenger (ﷺ) said, 'If one manumits his share of a jointly possessed slave, and can afford the price of the other shares according to the adequate price of the slave, the slave will be completely manumitted; otherwise he will be partially manumitted.' " (Aiyub, a sub-narrator is not sure whether the saying " ... otherwise he will be partially manumitted" was said by Nafi` or the Prophet.)