On the night of the 27th of Rajab The Prophet had a Mairaj. Concerning the virtue of this night Abu Huraira narrated The Prophet (peace and blessings of Allaah be upon him) said: Whoever fasts on 27th of Rajab. He will be rewarded with 60 month fast. On the same day, Gabriel came down to the Prophet with a message of Risalat. Sheikh Haibatullah has narrated from his teacher Abu Salma ( Salman Farsi ) that The Prophet said: There is a day and a night in the month of Rajab if one fasts on that day and worships that night. Then he will be rewarded for fasting for one hundred years and worshiping for one hundred nights. This is the night after which Rajab has three nights left. (Means 27th Rajab ) And this is the day on which Allah sent a message of Risalat to the Prophet.
It was the custom of Abdullah Ibn Abbas that when the 27th Rajab came, he would observe I’tikaaf. And after Zohar prayers, they would engage in reciting Nafl. After that he would recite four rakat nafil. And in each rakat he used to recite Surah Al-Fatihah once, Surah Al-Qadr three times, Surah Al-Ikhlas fifty times and then he would be engaged in Dua till the Asr prayer. He said that this was the custom of the Messenger of Allah.
It is narrated from Abu Hurayrah that, Whoever recite 12 rakah nafil on 27 Rajab with the intention of performing in such a way that after Surah Al-Fatihah three times Surah Al-Qadr and Surah Al-Ikhlas 12 times after this recite durood pak 1 time and 3 time this Dua.