It is reported from Sayyīdunā `Ali (r) that the Prophet (s) said: “Let all of you spend the night of mid-Sha`bān in worship (i.e. partly) and its day in fasting. For verily in it, Allah descends to the nearest heaven during this night, beginning with sunset, and says: Is there no one asking forgiveness that I may forgive them?
Imam al-Ghazali wrote in his Ihyā, The Night of mid-Sha`bān, in it [pray] 100 rakats, reciting in each raka`t after al-Fātiha, Surat al-Ikhlās 10 times; they never left it, as we related about the voluntary extra prayers and the Night of `Arafat…
Rajab is from the Sacred months and its days are written on the gates of the Sixth Paradise.
For every day of fasting [in Rajab], the worship of an entire year will be recorded in favor of the believer concerned, whose credit will be enhanced by a thousand degrees. If the believer keeps the fast throughout the whole of this month, as well as performing this particular salat-prayer, Allah will deliver that man or woman from the Fire of Hell and declare that he or she is entitled to enter the Garden of Paradise, therein to dwell in the vicinity of Allah (Glory be to Him).