Ibn ‘Abbas said that it was the custom of God’s messenger not to eat on the middle days* of the month whether travelling or not.
*Literally, the days of the white (nights). These are the days following the thirteenth, fourteenth, and fifteenth nights of the month, the nights when there is most moonlight.
He said that the Prophet used to fast on Mondays and Thursdays, and when someone remarked on this to him he said, “On Monday and Thursday God forgives every Muslim except two who are at variance, for He says they must be left till they make peace with one another.”
Narrated Hafsa said there were four things the Prophet never omitted:
fasting on ‘Ashura’, the first ten days of Dhul Hijja* and three days every month, and praying two rak'as before dawn.
*The Arabic has simply 'the ten', to be understood as translated above.
