صحیح ابن حبان
Ibn Hibban
كتاب الصوم
Book of Fasting
باب صوم التطوع - ذكر الأمر بصيام يوم عاشوراء إذ اليهود كانت تتخذه عيدا فلا تصومه
Chapter on Voluntary Fasting - Command to fast Ashura because Jews took it as a festival and did not fast it
1 hadith
Hadith 3627
Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) narrates: The Jews used to consider the day of Ashura as a festival. The Prophet (peace and blessings of Allah be upon him) said: You should act contrary to them; you should fast on (the day of) Ashura.