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.”

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ أَعْتَقَ جَارِيَتَهُ وَتَزَوَّجَهَا كَانَ لَهُ أَجْرَانِ