Hazrat Masruq (may Allah have mercy on him) said: The Messenger of Allah (peace and blessings be upon him) swore an oath to Sayyida Hafsa (may Allah be pleased with her) that he would not have relations with his slave woman and said: "She is forbidden to me." Then the command of expiation was revealed and it was ordered that you should not make unlawful what Allah has made lawful.