He said that when God’s messenger fasted on the day of ‘Ashura’ and commanded that it should be observed as a fast, he was told it was a day held in honour by Jews and Christians, and said, “If I am spared till next year I shall fast on the ninth.”
Ibn ‘Abbas said, "I never saw the Prophet singling out any day’s fast and considering it more excellent than another, except this day, the day of ‘Ashura’,* and this month, meaning the month of Ramadan."
*The 10th of Muharram.
Umm al-Fadl daughter of al-Harith said that on the day of 'Arafa some people near her argued about whether God’s messenger was fasting, some saying that he was and others saying that he was not. She therefore sent him a cup of milk while he was observing the halt at ‘Arafa on his camel, and he drank it.
Abu Huraira reported God’s messenger as saying, “The most excellent fast after Ramadan is in God’s month al-Muharram, and the most excellent prayer after what is prescribed is prayer during the night."