(6) باب فِي الرَّجُلِ يَعْتِقُ أَمَتَهُ ثُمَّ يَتَزَوَّجُهَا
Abu Dawud reported the Apostle of Allaah(ﷺ) as saying "Anyone who sets his slave girl free and then marries her, will have a double reward." (ID)
Reference (ID): Sunan Abi Dawud 2053 (ID)
In-book reference (ID): Book 12, Hadith 8 (ID)
English translation (ID): Book 11, Hadith 2048 (ID)