Nafi' narrates from Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The mudabbar slave is freed out of the third (of the estate)."
The correct version is mawquf (Ibn Umar's own statement), as al-Shafi'i (may Allah have mercy on him) narrated it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المدبر / 21574