1757. Fasting is Mustahab on every day of a year except those on which it is Haraam or Makrooh to observe a fast as mentioned. Some of them, which have been strongly recommended, are as follows:
recommended for him to give one Mudd of food or 12.6 Nukhud of silver to poor.
2.Thirteenth, fourteenth and fifteenth of every month.
3.On all days of Rajab and Sha’baan or on some days of these months even on one of its days.
4.The day of Eid Nourooz; from the 4th up to the 9th of the month of Shawwal. The 25th and 29th day of the month of Dhul Qa'dah. From the 1st day to the 9th day (i.e. ‘Arafa day) of the month of Dhul Hijja. However, if, it is not possible for one to recite the Duas of 'Arafa due to weakness caused by fasting, it is Makrooh to fast on that day. The auspicious day of Ghadir (18th Dhul Hijja). The auspicious day of Mubahila (24th Dhul Hijja). The 1st, 3rd, and 7th day of Muharram. The birthday of the Holy Prophet (17th Rabi' Al Awwal). 15th day of Jamadi Al – Awwal. 27th of Rajab - the day the Prophet (peace be upon Him) declared his Prophethood.
If a person observes a Mustahab fast, it is not obligatory on him to complete it. In fact, if one of his brother – in – faith invites him to a meal, it is Mustahab that he accepts the invitation and breaks the fast during the daytime.
 Nukhud: is a weighing scale for gold and silver in Shariah.