Musa bin Uqbah narrates from Nafi' that Abdullah bin Umar (may Allah be pleased with him) freed a slave of his, then made the condition that he would have his labour for some years, so he tended (livestock) for him for some of those years.
In the narration of the Qadi (may Allah have mercy on him): for part of a year. Then he came to him, either during Hajj or during Umrah, and Abdullah (may Allah be pleased with him) said to him: I have given up the condition I made with you; you are free and you owe no work. [Sahih]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21428