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.
Vol: 003 Book: 031 Hadith: 219
A Selected Dua
Glory is to Allah, and praise is to Allah, and Allah is the Most Great (each said thirty-three times). None has the right to be worshipped but Allah alone, He has no partner, His is the dominion and His is the praise...
-> Read More Info: Muslim 1/418, Whoever says this after every prayer will be forgiven his sins even though they be as the foam of the sea.