Ata narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) that a man freed his slave as a mudabbar, and he had no other wealth, so the Messenger of Allah (peace and blessings be upon him) sold him for 900 or 700 dirhams.
This is the correct (version).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المدبر / 21546