The month of Rajab is one of four months that are virtuous according to the Creator, Allah (Almighty). In Surah number 9, verse 36, Allah (swt) states, “The number of months with Allah has been twelve since the time he created the heavens and the earth. Four of them are sacred. That is the right religion. So do not wrong yourselves during them.”
In the last sermon the Prophet ﷺ said in his final speech to the people, “Indeed time has turned as it was the day Allah created the heavens and the earth. The year is 12 months, four of which are sacred. Three are consecutive, Dhul Qaeda, Dhul Hijjah, Al Muharram and Rajab (Mudar.) The one that falls between Jumada al-Thani and Shaaban.” This is by Bukhari, Muslim, Ahmad, Abu Dawood and Baihaqui.
Ibn Abbas (r.a) states, “Allah has selected and chosen four months then made them sacred and made their virtues to be the greatest. Sins committed in them would be greater than other times. He also made righteous good actions to be the greatest in them.”
K’aab (r.a) also states, “Allah has selected times and the most beloved to him are the four sacred months.”
Abu Yazeed (r.a) says, “Transgressions is to leave the obedience to Allah and acting upon what the Almighty has forbidden.”
It is the 7th month in the Hijri calendar and falls as the Prophet ﷺ states in his last sermon, “Between Jumada al-Thani and Shaaban.”
It was called Rajab because it was glorified by the people on the earth and the continuous glorification of the Malaika by it. Its link is also to the Arab tribe Mudar which use to show reverence and glory in it.
Mujeeba al-Baa’heleya reported that her father or uncle asked the Prophet ﷺ in which month, outside of the month of Ramadan, does fasting hold a greater reward? The Prophet ﷺ said to him, “Fast from the 4 sacred months.” And he repeated this statement 3 times. (Reported by Abu Dawood).
From this we understand some of the greatest, righteous first and second generation use to fast in the 4 sacred months and the most notable amongst them being Ibn Umar, Ali Hassan Al Basri, Abu Ishaak Al Siba’i and Sufyan Al Thawree who declares that, “The 4 sacred months, I love and prefer to fast in them.”
The days that are preferred for fasting are Monday and Thursdays, Wednesday and Thursdays and the white days. It is reported that the Prophet ﷺ has encouraged the fasting of these days. Hence it would be advisable to fast them in these sacred months.
Abu Hurairah reported that the Prophet ﷺ used to fast Monday and Thursday. He was asked, “Oh messenger of Allah, we see you fasting Monday and Thursday?” He replied “Indeed on Monday and Thursday, Allah forgives every Muslim, except the two who have animosity between them. Allah declares leave them until they make up.” (Ibn Ma’jah)
Abu Hurairah reported that the Prophet ﷺ said, “Actions are raised and declared on Mondays and Thursdays and I would love that my actions would be raised and declared whilst I am fasting.” (Tirmidhi)
The Prophet ﷺ was asked about fasts within year he states, “Fast in Ramadan and the 6 days that follow. Then every Wednesday and Thursday, hence you will be written as if you have fasted the whole year.” (Abu Dawood)
Ibn Umar reported that the messenger of God ﷺ states, “Whosoever fasts Wednesday, Thursday and Friday and once they have completed the fast, gives in charity any amount small or large. Allah will forgive their sins and the person will come out of his wrong doings as if he was reborn.” (Al Bahaqee)
Abu Hurayah states, “The prophet ﷺ advised me 3 things I should never neglect until I die. Fasting 3 days in each month. Praying Du’ha prayer regularly and that I pray my witr before I sleep.” (Bukhari and Muslim).
The great scholar Abd Al Qadir Al Jilani explains in details in his book (Al Gunya) the virtues of the month of Rajab. In his writings he encourages the Muslims to maximise their profit with Allah by doing extra optional worship during the month of Rajab. He reports in his book the following hadith:
Abu Thaar Al Gee’fari reported that the Prophet ﷺ states, “ Whosoever fasts the first day of Rajab it will be equivalent to fasting one month. And whomsoever fasts 7 days in the month of Rajab. The 7 doors of hell will be closed to them. And whomsoever fasts 8 days, the 8 gates of Ja’naah will be open for them. And whomsoever fasts 10 days Allah will exchange their bad deeds with good deeds. And whomsoever fasts 18 days a caller from the heaven says to them, Allah has forgiven you, continue the good work.”
Although the scholars agreed that their is nothing to confirm that fasting in the month of Rajab has been singled out by the Prophet ﷺ. However Rajab is one of the 4 sacred months. Which Allah (swt) has specified and commanded us that we should not wrong ourselves in them. Therefore the great scholars amongst the Tabiyeen encouraged their students to take notice and do the best they can in these months. By avoiding the forbidden and increasing optional acts of worship. Such as extra prayers, fasting, umrah and a lot of dua.