Khalid bin Dhikwan says: I asked Sayyida Rubayyi' bint Mu'awwidh (may Allah be pleased with her) about the fast of the day of Ashura. She said: The Messenger of Allah (peace and blessings be upon him) asked on the day of Ashura: "Which of you is fasting today?" The companions replied: "Some of us are fasting and some are not." He (peace and blessings be upon him) said: "Complete the fast for the rest of the day, and announce in the surroundings of Madinah as well that they too should fast for the remainder of the day."