Wrong.
The last verse was revealed on 10th Zul Hajj according to Sahih Bukhari.. Get your facts correct.
The Shia spend the entire eve of the 15th of Sha’ban in prayers and worship. Shia’s spend the 15th day in celebration, as it marks the birthday of their final Imām, Muhammad al-Mahdi. Shia’s believe him to be the Mahdi, an important figure who all the Muslims believe will rid the world of tyranny and injustice.
In this night, Narjes, the mother of Al-Mahdi and the grand-daughter of the Byzantine Emperor, gave birth to him at midnight. The story of Narjes summarized here, was considered from the dynasty of one of the Twelve “Hawaryin” who were the true followers of the Issa. The grandfather of Narjes, the Byzantine Emperor of the time, agreed to marry Narjes to several knights in turn. However, every time the palace was shaken during the marriage ceremony and the marriage then cancelled. One night, Narjes saw in a dream that Issa came with Mohammad and his grandchild, Imam Hassan Al-Askari (Askari - Arabic for soldier). She heard Muhammad asking Issa to marry Narjes for his grandchild, and Issa accepted in the ‘other place’. Narjes awoke frightened and decided to forget the dream. However, she frequently dreamt similar things and remained thinking of the matter. Once she saw Al-Zahraa, who told her to go into the Byzantine Army as a soldier to be captured. She told her that Imam Al-Hadi was going to buy her later on and marry her to his son , Al-Hassan Al-Askari. She did exactly and was captured to be sold at the slave market. Many tried to buy her but she always refused sharply, until Imam Al-Hadi sent a man from his side with a letter to her in her language. She agreed and went with him to Imam Al-Hadi. Some time later, she married Al-Hassan Al-Askari and soon she was pregnant with Al-Mahdi. The Abbassids had sent spies to watch for any pregnancy, since they were afraid of the promised Al-Mahdi. However, no signs appeared on Narjes until the night of the birth of Al-Mahdi. Al-Mahdi was given birth, and his parents saw him sitting on his knees and having a tattoo (a writing on his hand) which indicated that he was the promised rescuer.
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Many scholars and general people believe that Shab-e-Barat is not what it is believed to be. This belief is based on the fact that there is no mention of such a night in the Quran.**
Some quote 44.4 of the Quran to justify the Night from the Quran.
In the Indian subcontinent Muslims make sweets (especially Halwa or Zarda) to be given to the neighbors and the poor on the evening prior to the 15th of Sha’ban, but is deemed as an innovation to the faith by some Sunni scholars; some even consider it as a sin.
Even when hadiths are used to justify the night, some Sunni scholars (and again that is just some) have labeled such hadiths as weak (da’if).