Narrated from Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her): The Quraysh used to fast on the day of Ashura (the 10th of Muharram) during the days of ignorance. Then the Messenger of Allah (peace and blessings be upon him) also commanded fasting on this (day), until Ramadan was made obligatory. Then the Prophet (peace and blessings be upon him) said: Whoever wishes may fast on this day (Ashura), and whoever wishes may break the fast.

It is narrated from Hakam bin A'raj, he said: I came to Sayyiduna Ibn Abbas (may Allah be pleased with them), and he was sitting by the side of Zamzam, reclining on his cloak. So I said to him: Tell me about the fasting of 'Ashura. He said: When you see the crescent of Muharram, keep counting the days. Then when it is the ninth (9th) day, fast on that day. I said: Did the Messenger of Allah (peace and blessings be upon him) do the same? He said: Yes.

Narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Messenger of Allah (peace and blessings of Allah be upon him) came to Madinah, he saw that the Jews were fasting on the day of Ashura. So the Messenger of Allah (peace and blessings of Allah be upon him) asked them, "Why do you fast on this day?" They said, "This is a great day in which Allah Almighty saved Musa (peace be upon him) and the Children of Israel (from Pharaoh), and drowned Pharaoh and his people. Therefore, Musa (peace be upon him) fasted on this day out of gratitude, and we also fast." So the Prophet (peace and blessings of Allah be upon him) said, "We are closer and have more right to Musa (peace be upon him) than you." Then he (peace and blessings of Allah be upon him) fasted on that day and ordered his Companions to fast as well.

‘Ubaidullah bin Abi Yazid narrates that he heard from Sayyiduna Ibn Abbas (may Allah be pleased with them). He was asked about fasting on the day of ‘Ashura, so he said: I do not know that the Messenger of Allah (peace and blessings be upon him) fasted on any day, seeking the virtue of that day over other days, except this day, and of any month except the month of Ramadan (that is, among the days, he considered the day of ‘Ashura virtuous, and among the months, Ramadan).

Lady Rubayyi’ bint Mu’awwidh bin ‘Afra’ (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) sent an order on the morning of ‘Ashura to the settlements of the Ansar around Madinah that whoever has kept the fast should complete his fast, and whoever has eaten since morning should complete the rest of the day (i.e., should not eat anything now). After that, we used to fast and also made our small children fast as Allah willed, and we would go to the mosque and make cotton dolls for the children. Then, when any (child) cried for food, we would give him that (doll) to play with until the time of iftar came.

Sayyiduna Abu Salamah (may Allah be pleased with him) says: I asked Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) about the fasting of the Messenger of Allah (peace and blessings be upon him), so she said: The Messenger of Allah (peace and blessings be upon him) would fast so much that we would say he has fasted a lot, and he would refrain from fasting so much that we would say he has not fasted. And I did not see him fast in any month more than he fasted in Sha'ban. It was as if he fasted the entire month of Sha'ban. He would fast almost the whole of Sha'ban except for a few days.

It is narrated from Sayyiduna Imran bin Husain (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said to him or to someone else: "Did you fast any days at the beginning of Sha'ban?" He replied, "No." So the Prophet (peace and blessings be upon him) said, "When you have broken your fast, then fast for two days." (That is, when you have finished the month of Ramadan, then fast for two days.)

It is narrated from Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: Whoever fasts in Ramadan and then follows it with six days of fasting in Shawwal, it is as if he has fasted for the whole year.

Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says: I did not see the Messenger of Allah (peace and blessings of Allah be upon him) fasting during the ten days of Dhul-Hijjah.

Narrated from Sayyiduna Abu Qatadah (may Allah be pleased with him) that a man came to the Noble Prophet (peace and blessings be upon him) and asked, "How do you fast?" At this, the Prophet (peace and blessings be upon him) became angry (because this question was inappropriate; he should have asked, 'How should I fast?'). Then, when Sayyiduna Umar (may Allah be pleased with him) saw the Prophet's anger, he said, "We are pleased with Allah as our Lord, with Islam as our religion, and with Muhammad (peace and blessings be upon him) as our Prophet, and we seek refuge in Allah and His Messenger (peace and blessings be upon him) from anger." Sayyiduna Umar (may Allah be pleased with him) kept repeating these words until the Prophet's anger subsided. Then Sayyiduna Umar (may Allah be pleased with him) said, "O Messenger of Allah (peace and blessings be upon him)! What about the one who fasts every day?" The Prophet (peace and blessings be upon him) said, "He neither fasted nor broke his fast." Then he asked, "What about the one who fasts two days and breaks his fast one day?" The Prophet (peace and blessings be upon him) said, "Who has the strength for that?" Then he asked, "What about the one who fasts one day and breaks his fast one day?" The Prophet (peace and blessings be upon him) said, "This is the fast of Dawud (peace be upon him)." Then he asked, "What about the one who fasts one day and breaks his fast two days?" The Prophet (peace and blessings be upon him) said, "I wish I had the strength for that (meaning, this is also good if one has the strength)." Then the Messenger of Allah (peace and blessings be upon him) said, "Three fasts every month and the fasts of Ramadan, from one Ramadan to the next, this is like perpetual fasting (in reward)." And the fast of the day of Arafah, I hope from Allah that it will be an expiation for the sins of the previous year and the coming year, and from the fast of Ashura, I hope it will be an expiation for the previous year."