Month of mercy and forgiveness: Rajab

Rajab is the month of mercy and forgiveness. Being one of the months preceding Ramadan, Rajab is preparation for this period and Muslims should be engaged in spiritual purification and fast.
As for the fasting in the month of Rajab, Imam al-Nawawi in his book Sharh Sahih al-Muslim writes: “There is no direct command or prohibition to observe the fast in the month of Rajab. But the basis of fasting in this month remains as a desirable act.”
Then Imam al-Nawawi writes the following: “In the Sunan (collection of hadiths) of Abu Dawud, it is said that the Prophet (peace and blessings be upon him) urged him to fast in the forbidden months (ashhur al-hurum) and Rajab is one of them. Allah knows best.”
In this regard, Imam Khatib al-Shirbini in his book Mughni al-Muhtaj writes the following: “The best months for fasting after the month of Ramadan are the forbidden months, and the most auspicious of these is the month of Muharram, according to the hadith quoted by Imam Muslim: “After it (Muharram), the best month for fasting is Rajab.” (See: “Mughni al-Muhtaj” vol 3, p. 344].
“It is also reported from Aisha that the Messenger of God (peace and blessings be upon him) did not observe fasting after Ramadan, except for the months of Rajab and Sha’ban.”
This hadith indicates the desirability of fasting in the forbidden months in general.
Imam Ahmad said: “If a man fasts during that month, let him break the fast for one day in it, or two, just so as not to fast it all.”
This indicates that Imam Ahmad considered it preferable to observe fasting in the month of Rajab.
As for the opinion that the fast in the month of Rajab is an innovation, then regarding this ibn Hajar Al-Haithami in the book Fath al-Mubin (a commentary on the collection of the hadith of Imam Al-Nawawi “Al-Arba’un”) writes the following: “There is an opinion that the fast in the month of Rajab is an innovation, but it is not so. On the contrary, fasting in the month of Rajab is an excellent Sunna (desirable act), as I explained and stated in al-Fatawa al-Kubra.” (Fath al-Mubin, vol. 1, p. 226 / No. 5).
Based on the above, we can say that fasting in the month of Rajab is a desirable act for which a person receives great reward, since scholars of the Shafi’i madhhab, whose opinion is fundamental in the madhhab, refute the proposition that this is innovation, and there is no mention of its prohibition.