It is narrated from Hazrat Aisha (may Allah be pleased with her) that in the era of ignorance, the Quraysh used to fast on the tenth of Muharram, and the Prophet (peace and blessings be upon him) also used to fast on this day. After migrating to Madinah, the Prophet (peace and blessings be upon him) continued to fast on this day and instructed his companions (may Allah be pleased with them) to do so as well. Then, when the fasts of Ramadan were made obligatory, the Prophet (peace and blessings be upon him) began to fast only in Ramadan and abandoned the fast of Ashura. Now, whoever wishes may fast on this day, and whoever wishes may leave it.