“‘Allamah Ibn Dihya said in his Book: Adaa Ma Wajab min Bayaan wad’ al-Wadaa’eeen Fi Rajab (pg. 53-54):
“Some of the story tellers mention that the Isra occurred in Rajab and that is an absolute lie according to the People of praise and disparagement. Imam Abu Ishaaq al-Harbi said the Messenger (ﷺ) ascended on the night of twenty-seven in the month of Rabi’ al-Awwal. And we have mentioned what is in the issue of difference of opinion and evidences in our book entitled al-Ibtihaaj fi Ahaadith al-Mi’raaj”.
Shaikh al-Albani rahimahullah said in the notes on Adaa Ma Wajab min Bayaan wada’ al-Wadaa’eeen Fi Rajab (pg. 53):
“Hafidh ibn Hajr rahimahullah recorded that from the author [al-Harbi] in his treatise Tabayyan ul-‘Ajab Fi Ma warad Fi Rajab (pg. 3) and he affirmed it. Rather it is obligatory to clarify this to the people by any means possible and in every occasion [i.e. that it is not established]. And in Allah aid is sought.
I (Shaikh al-Albani) say: From that it is known that celebrating the Isra in Rajab is only based on a lie according to the testimony of the two Nobel Hafidhs [Hafidh Ibn Dihya and Hafidh Ibn Hajr may Allah have mercy upon them]. So no one should be deceived with what has spread in the latter generations that it occurred on twenty seventh of Rajab.
Along with the fact that the aforementioned celebration is not legislated in origin. This is because it is an innovation that was not done at the time of the Salaf like the remaining of the celebrations and anniversaries, whether they be for joy or sadness. It is not allowed to encourage/promote that by any means. Like speaking [about it] and writing that the night was in the month of Rajab, specifically on the twenty seventh. This is due to what it involves of misguidance and reassuring a lie to the people that the Isra occurred in Rajab and that it is legislated to celebrate it“.
[Qamoos al-Bid’ah pg. 719]
Faisal Ibn Abdul Qaadir Ibn Hassan