It is sunnah to fast on the occasion of Aashura i.e. 9th and 10th or 10th and 11th of Muharram. ^[1]

It is mustahab to fast on the following days:

1. The 13th, 14th and 15th of every Islamic month ^[2]

2. Six fasts during the month of Shawwaal ^[3]

3. Mondays and Thursdays ^[4]

4. The first nine days of Zul Hijjah. As far as the ninth of Zul – Hijjah is concerned, it is only mustahab for the one who is not performing hajj ^[5]

5. To fast every alternate day for the one who has the ability to do so. This fast is called Saum-e-Dawood, on account of Nabi Dawood (‘alaihis salaam) fasting in this manner ^[3]