‏الصيام : Hadeeth No:2522 Abu Musa (Allaah be pleased with him) reported: The day of 'Ashura was one which the Jews respected and they treated it as Id. The Messenger of Allaah (sallAllaahu alayhi wa sallam) said: You also observe fast on this day....

‏الفضائل : Hadeeth No:5717 This hadith has been transmitted on the authority of Anas with a slight variation of wording....