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.” Muslim transmitted it.
Reported by Muslim (No. 1134b), Ibn Majah (No. 1736) and Ahmad (No. 1869, 2002, 3044). Cited in Mishkat al-Masabih (No. 2041).
Ibn ‘Abbās (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) fasted on the Day of ‘Āshūrā', and ordered Muslims to fast on it.
وعن ابن عباس رضي الله عنهما أن رسول الله صلى الله عليه وسلم صام يوم عاشوراء، وأمر بصيامه. ((متفق عليه))
‘Abdullāh ibn ‘Abbās (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) said: "If I were to live till next year, I would definitely fast the ninth day."