It is reported about Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) that on the day of Ashura he said: "Fast on this day, for the Prophet (peace and blessings be upon him) commanded us to keep this fast."
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Mazidah bin Jabir, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5120
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«أخرجه المعجم الأوسط للطبراني برقم: 2642»