Teach me about Ashura in detail?
Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
'Ashura is the 10th day of Muharram. On this day Prophet Muhammad (Blessings and peace of Allah be upon him) fasted in Makkah with Quraish. When He migrated to àl-Madinah, he found the Jews fasting on this day. He continued fasting on that day and ordered the Muslims to fast too. Afterward Allah legislated the fasting during the Month of Ramadan. Then, the fast of 'Ashura became a supererogatory fast. But it is likable for a Muslim to fast on this day. If one fasts on this day, it is better to fast the 9th of Muharram also to oppose the Jews.
The pieces of evidence for this point are as follow:
1 - Imam al-Bukhari and Muslim narrated from 'Aisha ( may Allaah be pleased with her) that she said: "The tribe of Quraish used to fast on the day of 'Ashura in the pre-Islamic period, and Allah's Apostle too, used to fast on that day. When he came to al-Madinah, he fasted on that day and ordered others to fast too. Later, when fasting of the Month of Ramadah was prescribed, he (the Prophet) said: "Whoever wishes may fast -'Ashura- and whoever wishes may leave it" .
2 - Ibn Abbas related : When the Prophet Muhammad (Blessings and peace of Allah be upon him) came to Madinah, 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 Pharoah. Moses observed the fast on that day as a sign of gratitude to Allah. The Prophet Muhammad (Blessings and peace of Allah be upon him) said: "I am closer to Moses than them". So, he observed the fast (on this day) and ordered the Muslim to fast on it". [al-Bukhari and Muslim].
3 - It is reported in Sahihain (Bukhari and Muslim) from Ibn 'Abbas, he said: "I never saw the Prophet Muhammad (Blessings and peace of Allah be upon him) seeking to fast on a day more (preferable to him) than this day, (the day of 'Ashura) or this month, i.e. the month of Ramadan.
Imam al-Tirmizi narrated from Abu Qatadah that the Prophet Muhammad (Blessings and peace of Allah be upon him) said: "I hope from Allah that the fast on the day of 'Ashura atones for the sins of the preceding year."
Imam Ahmad narrated that "it atones the sins of two years, past and subsequent year".
4 - Imam Muslim narrated from Ibn Abbas, he said: "When the Messenger of Allah (Blessings and peace of Allah be upon him) fasted on the day of Ashura and commanded that it should be observed as a fast, they (his Companions) said to him: Messenger of Allah, it is a day which the Jews and Christians hold in high esteem. Thereupon, the Messenger of Allah (peace be upon him) said: When the next year comes, God willing, we would observe fast on the 9th . But the Messenger of Allah (Blessings and peace of Allah be upon him) died before the advent of the next year".
This is the guidance of the Prophet Muhammad (Blessings and peace of Allah be upon him) regarding to 'Ashura. His Companions and their followers went on this way. They have not distinguished this day by any practice except fasting.
But many acts done by some ignorant Muslims which "deform the face of Islam" have no evidence from Qur'an and Hadith. These acts include celebrating on this day, slapping one's face, tearing of one's clothes, using swords and blood-shedding. None of these acts have any authentic relevance to 'Ashura, but are among the innovations and bad deeds. The enemies of Islam use them to misrepresent Islam .
Allah knows best.