Is it disliked to fast specifically in the month of Rajab?
General Chapter
Al-Mughni
Book of Fasting
Primary text
It is disliked to single out the month of Rajab for fasting. Imam Ahmad states that if a man fasts in Rajab, he must break the fast for one or more days so that he does not fast the entirety of the month. The basis for this ruling is the tradition where Umar struck the hands of those preparing for Rajab fasting, instructing them to eat, stating that Rajab was a month venerated by the Jahiliyyah (pre-Islamic ignorance). Furthermore, traditions from Ibn Umar indicate that when he saw people preparing for Rajab, he disliked it, advising them to fast some days and break the fast on others. A similar narration exists from Ibn Abbas. Another tradition recounts Abu Bakrah destroying new baskets and water jars used for Rajab fasting, questioning why they treated Rajab like Ramadan.
Supporting text
Imam Ahmad stipulated that if an individual customarily fasts throughout the entire year, they may fast in Rajab, but otherwise, one must not fast it continuously, but rather break the fast within it so as not to resemble Ramadan.