Question 179: There are days on which we voluntarily observe Sawm (Fast) during Rajab. Should these days be in the beginning, middle, or end of the month?
Answer: No specific Hadeeths were authentically reported about the merit of Sawm in Rajab, except that which was related by Al-Nasaa’ee and Aboo Daawood, and ranked as Saheeh (authentic) by Ibn Khuzaymah, on the authority of Usamah who said: I asked, ‘O Messenger of Allaah, I have not seen you fast in a month as much as you fast in Sha‘baan.’ He (peace be upon him) said, ‘This is a month between Rajab and Ramadaan that people overlook. It is a month in which deeds are raised to the Lord of the worlds, and I love that my deeds be raised while I am fasting.’ General Hadeeths were mentioned about encouraging Sawm for three days of every month; Sawm on the White Days,which are the 13th, 14th, and 15th of every Hijree (lunar) month; Sawm in the Sacred, Inviolable Months; and Sawm every Monday and Thursday. The same applies to the month of Rajab. If you are keen on choosing some days to fast on, you can fast on the White Days or Mondays and Thursdays. Otherwise, the matter is open to choice. As for dedicating certain days in Rajab to Sawm, we do not know of any basis for it in Sharee‘ah (Islaamic law)... read more here.