Day of Ashurah
According to tradition, when the Prophet Muhammad (May the blessings and the peace of God be upon him) led his followers to Medina, he found the Jews of that area fasting on the day of Ashurah (10th of Muharram) in rememberance of Moses and the Children of Israel being saved from the Pharaoh. Prophet Muhammad then remarked "We have more right, and we have a closer connection with Moses than you have", so he observed fast (on the day of 'Ashura), and gave orders that it should be observed. It was commanded so until Ramadan became obligatory, in which it is now recommended to observe fast but not obligatory.
{mospagebreak title=Hadiths} Narrated Ibn 'Abbas:
When the Prophet came to Medina, he found (the Jews) fasting on the day of 'Ashura' (i.e. 10th of Muharram). They used to say: "This is a great day on which Allah saved Moses and drowned the folk of Pharaoh. Moses observed the fast on this day, as a sign of gratitude to Allah." The Prophet said, "I am closer to Moses than they." So, he observed the fast (on that day) and ordered the Muslims to fast on it.
Translation of Sahih Bukhari; Volume 4, Book 55, Number 609
'A'isha (Allah be pleased with her) reported
that the Quraish used to observe fast on the day of Ashura during the pre-Islamic days. The Messenger of Allah (may peace be upog him) then commanded to fast on that day till (fasting) in Ramadan became obligatory. Then the Messenger of Allah (may peace be upon him) said: He who wished to fast should do so. and he who wished to break it may do so.
Translation of Sahih Muslim; Book 006, Number 2503
Narrated 'Aisha:
'Ashura' (i.e. the tenth of Muharram) was a day on which the tribe of Quraish used to fast in the pre-lslamic period of ignorance. The Prophet also used to fast on this day. So when he migrated to Medina, he fasted on it and ordered (the Muslims) to fast on it. When the fasting of Ramadan was enjoined, it became optional for the people to fast or not to fast on the day of Ashura.
Translation of Sahih Bukhari; Volume 5, Book 58, Number 172
Ibn'Abbas (Allah be pleased with both of them) reported
that the Messenger of Allah (may peace be upon him) arrived in Medina and found the Jews observing fast on the day of 'Ashura. The Messenger of Allah (may peace be upon him) said to them: What is the (significance) of this day that you observe fast on it? They said: It is the day of great (significance) when Allah delivered Moses and his people, and drowned the Pharaoh and his people, and Moses observed fast out of gratitude and we also observe it. Upon this the Messenger of Allah (may peace be upon him) said: We have more right, and we have a closer connection with Moses than you have; so Allah's Messenger (may peace be upon him) observed fast (on the day of 'Ashura), and gave orders that it should be observed.
Translation of Sahih Muslim; Book 006, Number 2520:
Narrated 'Aisha:
The people used to fast on 'Ashura (the tenth day of the month of Muharram) before the fasting of Ramadan was made obligatory. And on that day the Ka'ba used to be covered with a cover. When Allah made the fasting of the month of Ramadan compulsory, Allah's Apostle said, "Whoever wishes to fast (on the day of 'Ashura') may do so; and whoever wishes to leave it can do so."
Translation of Sahih Bukhari; Volume 2, Book 26, Number 662
Narrated 'Aisha:
Allah's Apostle ordered (the Muslims) to fast on the day of 'Ashura', and when fasting in the month of Ramadan was prescribed, it became optional for one to fast on that day ('Ashura') or not.
Translation of Sahih Bukhari; Volume 3, Book 31, Number 219
Narrated 'Aisha:
(The tribe of) Quraish used to fast on the day of Ashura' in the Pre-lslamic period, and then Allah's Apostle ordered (Muslims) to fast on it till the fasting in the month of Ramadan was prescribed; whereupon the Prophet said, "He who wants to fast (on 'Ashura') may fast, and he who does not want to fast may not fast."
Translation of Sahih Bukhari;Volume 3, Book 31, Number 117
{mospagebreak title=Sources} Translation of Sahih Bukhari
Translation of Sahih Muslim, Book 6: The Book of Fasting (Kitab Al-Sawm)