Sahih Bukhari Volume 5, Book 59, Hadith Number 676.

Narrated By Abu Huraira : When I came to the Prophet said on my way, “O what a long tedious tiresome night; nevertheless, it has rescued me from the place of Heathenism.” A slave of mine ran away on the way. When I reached the Prophet I gave him the oath of allegiance (for Islam), and while I was sitting with him, suddenly the slave appeared. The Prophet said to me. “O Abu Huraira! Here is your slave,” I said, “He (i.e. the slave) is (free) for Allah’s Sake,” and manumitted him.