Nafi' (may Allah have mercy on him) narrates from Ibn Umar (may Allah be pleased with them both) that the mudabbar slave is freed out of the third (of the estate).
Al-Shafi'i (may Allah have mercy on him) said: Ali bin Zabyan told me: "I used to narrate it as marfu' (from the Prophet), but my companions said to me: 'It is not marfu'; it is mawquf on Ibn Umar.' So I narrated it as mawquf." And the hadith masters (huffaz) narrate it as mawquf on Ibn Umar.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المدبر / 21573