Al-Maqburi heard Sayyiduna Abu Hurayrah (may Allah be pleased with him) say: Were it not for two matters, I would love to be a slave owned by another, because a slave has no authority to dispose of his own property; and I heard the Messenger of Allah (peace and blessings be upon him) say: "Allah has not created a slave who fulfils the right of Allah upon him and the right of his master except that Allah gives him his reward twice."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10774