Ata (may Allah have mercy on him) narrated from Sayyiduna Jabir (may Allah be pleased with him) that a man freed his slave as a mudabbar; then he fell into need, so the Messenger of Allah (peace and blessings be upon him) took that slave and said: "Who will buy this slave from me?" Nu'aym bin Abdullah (may Allah be pleased with him) bought him for 800 dirhams, and he (peace and blessings be upon him) gave the price back to the owner.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المدبر / 21542