1. It falls on the 10th of Muharram
The day of Ashura falls on the 10ht of Muharram, and its name derives from the Arabic word ' Asharah', which literally means ten. Muharram is also the only month which has Allah's name attached to it, as such, the Prophet (saw) referred to it as the 'Sacred Month of Allah'.
2. Fasting on Ashura wipes out sins of the previous year
When the Prophet (saw) arrived in Madina, he (saw) found the Jews observing the fast on the day of Ashura. The Prophet (saw) asked them about it and they replied, 'This is the day Musa became victorious about Firoun'. The Prophet (saw) then said to the Muslims , 'We are nearer to Musa so fast on this day'. [Bukhari]
However, then he (saw) encouraged us to fast on the 9th or 11th of Muharram too to differentiate his ummah from the People of the Book.
3. Giving charity on Ashura is equal to giving charity for an entire year
On the authority of 'Abdullah bin 'Amr bin al-'As )may Allah be pleased with both of them) it is believed that the Prophet (saw) said, "Whoever fasts 'Ashura' it is as if he has fasted the entire year. And whoever gives charity this day it is like the charity given for an entire year". [Ibn Rajab's Lata'if al-Ma'arif)
4. The Kiswah of the Ka'ba used to be changed on 'Ashura'
The Kiswah of the Ka'ba is now donned during the month of Dhul Hijjah, however, previously Muslims used to practice this custom on the day of Ashura.
‘On the authority of ’Aishah (ra) who said, “The people used to fast on Ashura before the fasting of Ramadan was made obligatory. And on that day the Ka‘bah used to be covered with a cover. When Allah made the fasting of the month of Ramadan compulsory, Allah’s Messenger (saw) said, ’Whoever wishes to fast (on the day of ‘Ashura’) may do so; and whoever wishes to leave it can do so”’. (Bukhari)
5. It is encouraged to spend on one's family on Ashura
Apart from the virtue of fasting on the day of Ashura, the Prophet (saw) used to encourage one to be generous upon their family on this day.
6. Musa (as) and the Israelites were saved from Firoun on Ashura
’Then We inspired to Musa [as], “Strike with your staff the sea,” and it parted, and each portion was like a great towering mountain. And We advanced thereto the pursuers. And We saved Musa [as] and those with him, all together. Then We drowned the others. Indeed in that is a sign, but most of them were not to be believers. And indeed, your Lord - He is the Exalted in Might, the Merciful’. (Qur’an, 26:63-68)
7. Nuh’s (as) Ark landed on Mount Judiyy (modern day Turkey) on Ashura
‘In a narration reported by Imam Ahmad (rh), it was on this day that the Ark of Nuh (as) came to rest on Mount Judiyy’. (Tafsir Ibn Kathir)
‘And it was said, “O earth, swallow your water, and O sky, withhold [your rain]”. And the water subsided, and the matter was accomplished, and the ship [the ark of Nuh (as)] came to rest on the [mountain of] Judiyy. And it was said, “Away with the wrongdoing people”’. [Qur’an, 11]