The Messenger of Allah ﷺ said, "Three people will receive a double reward. Among them is a man who had a slave-girl, raised her well, taught her well, then freed her and married her. He will have two rewards."
قال رسول الله ﷺ: ثلاثة لهم أجران منهم: رجل كانت عنده أمة فأدبها فأحسن تأديبها، وعلمها فأحسن تعليمها، ثم أعتقها، فتزوجها، فله أجران.