Musannaf Ibn Abi Shaybah 9610 — Fasting the day of Ashura

Abd al-Rahman bin Yazid said: Once Sayyiduna al-Ash'ath bin Qays (may Allah be pleased with him) came to Sayyiduna Abdullah (may Allah be pleased with him). Sayyiduna Abdullah was eating, and he invited al-Ash'ath bin Qays to eat too. He said: "Is today not the day of Ashura?" Sayyiduna Abdullah asked: "Do you know what the day of Ashura is?" He asked: "What is it?" Sayyiduna Abdullah said: "It is the day on which the Messenger of Allah (peace and blessings be upon him) used to fast before Ramadan was made obligatory; when the fasts of Ramadan were made obligatory, he stopped fasting on this day."