The Prophet ﷺ said, "The right of patronage belongs to the one who freed the slave."
حدثنا حماد بن خالد حدثنا مالك عن نافع
أن النبي ﷺ قال الولاء لمن أعتق
No references are available.
Its isnad is sahih. It appears at greater length in Muwatta 3:9, narrated from Nafi from Ibn Umar. It has already appeared at length via the route of Malik at 5929. It has also appeared repeatedly, both abridged and at length, most recently at 6313 and 6415.