It is narrated from Sayyida Umm Salama (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) used to fast on Saturdays and Sundays more frequently than on other days on which he would fast. He (peace and blessings be upon him) also said regarding them: "These are the festival days of the polytheists, that is, the Jews and Christians, and I wish to oppose them."