Sayyidah Aisha (may Allah be pleased with her) said: The Quraysh used to fast on the day of Ashura in the pre-Islamic period. Then the Messenger of Allah (peace and blessings be upon him) also ordered fasting on this day, until the fasting of Ramadan was made obligatory. Then the Messenger of Allah (peace and blessings be upon him) said: Whoever wishes may fast on the day of Ashura, and whoever wishes may leave it.

Sayyiduna Abdullah bin Umar (may Allah be pleased with them) narrated that in the days of ignorance, we used to fast on the day of Ashura, but when the fasting of Ramadan was prescribed, the Prophet (peace and blessings of Allah be upon him) said: Whoever wishes may fast on Ashura, and whoever wishes may leave it.

Sayyiduna Ash'ath (may Allah have mercy on him) came to Sayyiduna Abdullah bin Mas'ud while he was eating. Ash'ath said, "Today is the day of 'Ashura." Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said, "In those days, the fast of 'Ashura was observed before the fasting of Ramadan was prescribed, but when the command for fasting in Ramadan was revealed, this fast was abandoned. Come, you also join in the meal."

Humaid bin Abdur Rahman narrates that I heard Sayyiduna Muawiyah bin Abi Sufyan (may Allah be pleased with him) on the day of Ashura during Hajj, delivering a sermon from the pulpit. He said: O people of Madinah, where have your scholars gone? I heard the Messenger of Allah (peace and blessings be upon him) say: This is the day of Ashura; its fasting is not obligatory upon you, but I am fasting, so whoever wishes may fast (and act upon my Sunnah), and whoever wishes may not fast.

Sayyiduna Ibn Abbas (may Allah be pleased with them) narrated that when the Prophet (peace and blessings of Allah be upon him) came to Madinah (in the second year), he saw the Jews fasting on the day of Ashura. He inquired from them about the reason for this. They replied that this is a good day; on this day Allah Almighty saved the Children of Israel from their enemy (Pharaoh), so Musa (peace be upon him) fasted on this day. The Prophet (peace and blessings of Allah be upon him) said, "We are more deserving of following Musa (peace be upon him) than you." Thus, he fasted on that day and ordered his Companions to do so as well.

Sayyiduna Abu Musa (may Allah be pleased with him) narrated that the Jews considered the day of Ashura as a festival, so the Messenger of Allah (peace and blessings be upon him) said: "You should also fast on this day."

Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that I did not see the Prophet Muhammad (peace and blessings be upon him) deliberately fasting on any day, considering it superior to other days, except for the day of Ashura and this month of Ramadan.