Ashoura Fasting

Assalaamu 'alaykum!

This is a reminder to try to fast tomorrow and the day after tomorrow (Monday and Tuesday), which are the 9th and 10th (i.e., Ashura) of Muharram.
Rasoolullaah (saws) indicated that fasting on Ashura wipes away the sins [i.e., minor ones] of the past year and to fast the day before with it as well.
May Allah (swt) make it easy, accept our fasts, and bestow His mercy and blessings upon all of us! Aameen!

Fasting on the Day of Ashura, I hope will expiate the sins of the previous year.
(Sahih Muslim)

The fast of Ashura falls on the 10th day of Muharram. However, it is also encouraged for Muslims to fast a day before and after Ashura, i.e. 9th and 11th Muharram as well.
The Prophet s.a.w said in a hadith:

"Fast on the day before and the day after Ashura.
(Musnad Ahmad)

Imam Ibn Al-Qayyim mentioned that there are three levels of fasting on Ashura, the first one being the best and most complete, followed by the other degrees accordingly:
1. Fasting for 3 consecutive days on the 9, 10 & 11 Muharram. (Monday - Tuesday - Wednesday)
2. Fasting on 9 and 10 Muharram only (Monday - Tuesday).
3. Fast on the 10th of Muharram only (Tuesday).

However, there is no obligation. In fact, you may also fast on both the 10th and 11th Muharram (Tuesday - Wednesday). Feel free to perform what is most convenient and feasible for you.

More info:https://muslim.sg/articles/fasting-on-the-day-of-ashura