Is it Sunnah to fast in the month of rajab? Can i fast?

The month of Rajab is one of the sacred months of which Allaah says (interpretation of the meaning):
“Verily, the number of months with Allaah is twelve months (in a year), so was it ordained by Allaah on the Day when He created the heavens and the earth; of them four are Sacred (i.e. the 1st, the 7th, the 11th and the 12th months of the Islamic calendar). That is the right religion, so wrong not yourselves therein”
[al-Tawbah 9:36]

With regard to fasting the month of Rajab, there is no saheeh hadeeth to indicate that there is any special virtue in fasting all or part of this month or just on 27th day of this month.What some people do, singling out some days of Rajab for fasting, believing that they are better than others, has no basis in sharee’ah.

But there is a report from the Prophet (peace and blessings of Allaah be upon him) which indicates that it is mustahabb to fast during the sacred months (and Rajab is one of the sacred months). The Prophet (peace and blessings of Allaah be upon him) said: “Fast some days of the sacred months and not others.” Narrated by Abu Dawood, 2428; classed as da’eef by al-Albaani in Da’eef Abi Dawood.

Even if this hadeeth were saheeh, it indicates that it is mustahabb to fast during the sacred months. So if a person fasts during Rajab because of this, and he also fasts in the other sacred months, there is nothing wrong with that. But singling out Rajab for fasting is not right.

Fasting in Rajab is no better than fasting in any other month, except that it is one of the sacred months. There is no report in the saheeh Sunnah to suggest that there is anything special about fasting in this month.

 Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked about fasting on the twenty-seventh of Rajab and spending that night in prayer. He replied: Fasting on the twenty-seventh of Rajab and spending that night in prayer is a bid’ah (innovation), and every bid’ah is a going astray.