From Sahih Bukhari (Hadith 2141):
Narrated Jabir bin `Abdullah:A man decided that a slave of his would be manumitted after his death and later on he was in need of money, so the Prophet (ﷺ) took the slave and said, "Who will buy this slave from me?" Nu'aim bin `Abdullah bought him for such and such price and the Prophet (ﷺ) gave him the slave
Reference: Bukhari 2141