Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) commanded fasting on the day of Ashura, and he himself did not keep this fast.
Abu Ya'la recorded it. Its chain contains a narrator, Abu Harun al-Abdi, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5117