“The month of Rajab has no Sunnan (supererogatory acts of worship following the example of the Prophet) specifically for it. Yet, there is nothing wrong with performing ‘Umrah (lesser pilgrimage) during it, because the Salaf (righteous predecessors) used to perform ‘Umrah during Rajab. Ibn ‘Umar (may Allah be pleased with them both) is authentically reported to have said:
The Prophet (peace be upon him) performed ‘Umrah in the month of Rajab.
Therefore, there is nothing wrong with performing ‘Umrah in Rajab, whereas associating any other act of worship with it is baseless in Shari‘ah (Islamic law). This month is like the rest of the months i.e. one can offer Salah (Prayer), fast the three days of every month, or fast Mondays and Thursdays as one does in all the other months, without assigning to it a particular act of worship, with the exception of ‘Umrah in Rajab, for there is nothing wrong with doing it.”
[Fatwas of Nur `Ala Al-Darb, the fatwa seen here]
AbdulFattaah Bin Uthman