From Sahih Bukhari (Hadith 2403):
Narrated Jabir bin `Abdullah:A man pledged that his slave would be manumitted after his death. The Prophet (ﷺ) asked, "Who will buy the slave from me?" Nu'aim bin `Abdullah bought the slave and the Prophet (ﷺ) took its price and gave it to the owner
Reference: Bukhari 2403