لَيْلَةٍ مُّبَارَ‌كَةٍ 'blessed night', in verse 2 according to majority of the Commentators, refers to 'laylatul Qadr' or the 'Night of Power' which occurs in the last ten nights of the month of Ramadan. During this night Allah sends down countless blessings for his slaves/servants. It has been explicitly mentioned in Surah Al-Qadr, thus:

إِنَّا أَنزَلْنَاهُ فِي لَيْلَةِ الْقَدْرِ‌

"We sent it (the Qur'an) down in the Night of Qadr". (97:1)

This clearly indicates that the phrase 'laylah mubarakah' (blessed night) occurring in the verse refers to the 'Night of Power'. It is narrated in a Tradition of the Prophet ﷺ that all Prophets (علیہم السلام) since the inception of man till the end, received their respective Books in the month of Ramadan on different dates. Sayyidna Qatadah ؓ reports on the authority of Sayyidna Wathilah ؓ that the Messenger of Allah ﷺ said that Prophet Ibrahim (علیہ السلام) received his Scriptures on 1st Ramadan, Torah was revealed on 6th Ramadan, Zabur was revealed on 12th Ramadan, Injil was revealed on 18th Ramadan and the Holy Qur'an was revealed on the night of 24th, that is, on 25th Ramadan. (Qurtubi).

The statement that the Qur’ an was revealed in the Night of Power’ means that it was revealed in its entirety from the Preserved Tablet to the lowest Firmament in one night of the month of Ramadan. But, it was revealed to the Prophet ﷺ gradually over a period of twenty-three years. Some scholars have expressed the opinion that the installment of the Qur'an that was destined to be revealed in a given year used to be sent down on the Night of Power from the Preserved Tablet to the Firmament of the Earth. (Qurtubi).

Some other scholars of Tafsir, like ` Ikrimah ؓ ، interpret the phrase 'laylah mubarakah' (blessed night) as referring to 'laylat-ul-bara'ah' (the Night of Immunity), that is, the 15th night of Sha` ban. But to say that the Qur'an was revealed during this night goes against the clear texts of the Qur'an: In شَهْرُ‌ رَ‌مَضَانَ الَّذِي أُنزِلَ فِيهِ الْقُرْ‌آنُ ! and in إِنَّا أَنزَلْنَاهُ فِي لَيْلَةِ الْقَدْرِ‌ we come across "The month of Ramadan is the one in which the Qur'an was revealed...(2:185) " and "We have sent it (the Qur'an) in the Night of Qadr - (97:1) ". In the presence of such clear texts, it cannot be accepted, without any strong evidence, that the Qur'an was revealed in the Night of Immunity. There are, however, certain Traditions that speak highly of this night - that it is a night of blessings and that it is a night during which Allah showers His mercy. Some versions of the Tradition use exactly the same words as the Qur'an uses in the verse to describe 'laylah mubarakah' فِيهَا يُفْرَ‌قُ كُلُّ أَمْرٍ‌ حَكِيمٍ أَمْرً‌ا مِّنْ عِندِنَا . "In that (night), every wise thing is decided (4) through a command from Us...(5) ". In interpreting this verse Sayyidna Ibn ` Abbas ؓ says that it refers to the Night of Power, in which the Qur'an was revealed. In it all matters are decreed to happen from the present Night of Power to the next, relating to all creation, their births, their deaths, their provisions and other details. Other leading authorities on Tafsir, like Sayyidna Hasan, Qatadah, Mujahid and others ؓ concur with Sayyidna Ibn ` Abbas ؓ . Mahdawi says that all matters decreed by Allah are, on this night, transferred to the angelic scribes who record the decrees of the coming year. Other texts of Qur'an and Sunnah bear testimony to the fact that Allah had decreed all matters in pre-eternity (azal) even before the creation of man. Therefore, the statement that man's destiny is decreed in this night simply means that the decrees for the whole year are handed over, in this night, to the relevant angels for implementation. (Qurtubi).

Because some versions of the Tradition state that births, deaths and sustenance are decreed in the night of immunity or 15th night of Sha'ban, some of the scholars have interpreted the phrase 'laylah mubarakah' in the current verse as referring to 'laylat-ul-bara'ah' or 'the Night of Immunity'. But this is not correct, because here the revelation of the Qur'an is mentioned first; and its revelation in the month of Ramadan is confirmed by the clear texts of the Qur'an. Some versions state that sustenance and other things are decreed in the Night of Immunity. Ibn Kathir, first of all, says this Tradition is mursal and such Tradition cannot be reliable in the presence of clear/express texts. Qadi Abu Bakr Ibn ` Arabi asserts that no authentic Tradition relating to mid-Sha'ban is available which may show that sustenance, births and deaths are determined and decreed in that night. He further rejects the idea that there is any reliable Tradition on the merit of this night. Ruh-ul-Ma` ani, however, cites a Tradition, without a chain of transmitters, narrated by Sayyidna Ibn ` Abbas ؓ in which he says that sustenance, life and death are determined in the mid-Sha'ban night, and in the Night of Power the decrees are handed over to the angels. If this Tradition is confirmed, then the two interpretations can be reconciled and synchronized. Otherwise, the express words of Qur'an and authentic Traditions relating to 'laylah mubarakah' and 'fiha yufraqu...' in the verse of Surah Dukhan فِيهَا يُفْرَ‌قُ clearly show that they refer to the 'Night of Power'. As far as the merit of the night of mid-Sha'ban is concerned, it is a separate issue. Some Traditions do speak about it but they are weak. Therefore, Qadi Abu Bakr Ibn ` Arabi denied any merit of this night. Chains of Transmission of Traditions concerning mid-Sha'ban are all weak but, it may be suggested that, if the various ways of transmission are put together, they gain strength. Therefore, many great scholars have accepted the Traditions about mid-Sha'ban because there is room to act upon weak Traditions relating to meritorious actions. Allah knows best!