According to mine point of view and read some articles about that “what is the importance of observe fast on Ashura’s day†we should must observe the fast on 9th and 10th Muharram ul Haram.
This is not mandatory to observe fast on 9th and 10th muharram but our prophet (BPUH) always gave preference do the fast on this day because on that day, a very important incident occur when Hazart Moses (A.S) had given a great favor by Allah almighty.
The history behind fasting on Ashura
Jews fasting on this day of Ashura:
When prophet (BPUH) FROM MAKKHA to MADEEN. He noticed that Jew do the fast on the first month (10 muharram) in the remembrance and gratitude of Allah almighty as prophet mosa (A.S) was also fasting when Allah saved him and his people from the evil of pharaoh at that time.
So prophet (PBUH) started fasting on this day and same insisting to his followers.
“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. I am closer to Moses than they.†So phrphet (PBUH) started observing fasting on this day-ibn abbas (sahih al-bukhari hadith- 4.609)
9th and 10th muharram is not only for shay’s sect as precious for all Muslims like for Sunni and other sects.
The importance of fasting on the day of ASHURA:
“Fasting the day of ‘ashoora’(is of great merit) I hope that Allah almighty will accept it as an expiation for the previous day.â€- MUSLIMS
“I never saw Allah’s messenger (PBUH) so keen to fast any day and give it priority over any other than this day, the day of ashoora and month meaning Ramadan.†– Ibn ‘Abbas – (Al-Bukhari)
“I seek from Allah that fasting on the day of Arafah may atone for the sins of the preceding and the coming years, and I seek from Allah that fasting on the day of Ashura may atone for the sins of the preceding year.â€Â – Narrated by Abu Qatadah (Sahih Muslim Hadith – 564)