Shab-e-Meraj is the night of blessing. The word Me’raj (Ascent of Prophet Muhammad (PBUH) is derived from Urooj, which means, ‘height’, ‘ascension’. It occurs in Hadith. The Qur’anic word for the event is ‘Israa’, meaning ‘the journey’.
Angel Jibriel along with two other angels visited the holy Prophet (PBUH) one night, while He (PBUH) was asleep in the Hateempart of Ka’abah. The angel then operated upon His (PBUH) heart and made some changes probably because the material body could not withstand the space travel with the required velocity without certain protection. By incorporating the changes in the body system, his body was probably converted from material into Noorani (lightening) body to withstand the journey of space. After the transformation of the body, a conveyance named Burraq was presented before him. Burraq, the narration says, resembled a horse-like animal but its very name indicates that it also possessed a lightening body. The word Burraq is derived from the root Bar’q which means ‘electricity’ in Arabic. Burraq signifies that he had to be taken with the velocity of Bar’q that is electricity or light which is 300,000 km per second.
No wonder, within no time he reached Baitul Maqdis or Masjid-e-Aqsa. In Baitul Maqdis, the Prophet (PBUH) led in prayer, all the earlier Prophets who were gathered for the occasion. From there, he was raised to the heavens where he again met and conversed with different Prophets. Then came the most honored moment of the journey as He (PBUH) was elevated to a point beyond heavens called Sidrat-ul-Muntaha. There has been difference of opinion among scholars right from the days of Sahaba about whom the Prophet (PBUH) met and saw at the place beyond heavens and horizon. Some say he saw Allah while others opine that he saw Jibriel in his original form.
About the celebration, I must point out that there is not a single Hadith or authentic narration certifying the popular belief about 27th Rajab being the date of Me’raj. There are differences among scholars regarding the date, month and also the year of Me’raj. However, there is nothing against praying and glorifying the Lord and remembering the Prophet (PBUH) on a particular night. At worst, it would be a distortion of a date in history, if the date is not actually true. It certainly is not a Bid’at unless the prayers of 27th Rajab are assumed to be obligatory part of Deen.