Allah tells us that He revealed the Magnificent Qur'an on a blessed night, Laylatul-Qadr (the Night of Decree), as He says elsewhere:
﴿إِنَّا أَنزَلْنَـهُ فِى لَيْلَةِ الْقَدْرِ ﴾
(Verily, We have sent it down in the Night of Al-Qadr) (97:1). This was in the month of Ramadan, as Allah tells us:
﴿شَهْرُ رَمَضَانَ الَّذِى أُنزِلَ فِيهِ الْقُرْآنُ﴾
(The month of Ramadan in which was revealed the Qur'an) (2:185). We have already quoted the relevant Hadiths in (the Tafsir of) Surat Al-Baqarah, and there is no need to repeat them here.
﴿إِنَّا كُنَّا مُنذِرِينَ﴾
(Verily, We are ever warning.) means, telling them what is good for them and what is harmful for them, according to Shari`ah, so that the proof of Allah may be established against His servants.
﴿فِيهَا يُفْرَقُ كُلُّ أَمْرٍ حَكِيمٍ ﴾
(Therein (that night) is decreed every matter, Hakim.) means, on Laylatul-Qadr, the decrees are transferred from Al-Lawh Al-Mahfuz to the (angelic) scribes who write down the decrees of the (coming) year including life span, provision, and what will happen until the end of the year. This was narrated from Ibn `Umar, Mujahid, Abu Malik, Ad-Dahhak and others among the Salaf.
(Hakim) means decided or confirmed, which cannot be changed or altered. Allah says:
﴿أَمْراً مِّنْ عِنْدِنَآ﴾
(As a command from Us.) meaning, everything that happens and is decreed by Allah and the revelation that He sends down -- it all happens by His command, by His leave and with His knowledge.
﴿إِنَّا كُنَّا مُرْسِلِينَ﴾
(Verily, We are ever sending,) means, to mankind, sending Messenger who will recite to them the clear signs of Allah. The need for this was urgent.
﴿رَحْمَةً مِّن رَّبِّكَ إِنَّهُ هُوَ السَّمِيعُ الْعَلِيمُ رَّبُّ السَّمَـوَتِ وَالاٌّرْضِ وَمَا بَيْنَهُمَا﴾
((As) a mercy from your Lord. Verily, He is the All-Hearer, the All-Knower. The Lord of the heavens and the earth and all that is between them,) means, the One Who sent down the Qur'an is the Lord, Creator and Sovereign of the heavens and the earth and everything in between them.
﴿إِن كُنتُمْ مُّوقِنِينَ﴾
(if you (but) have a faith with certainty.) Then Allah says:
﴿لاَ إِلَـهَ إِلاَّ هُوَ يُحْىِ وَيُمِيتُ رَبُّكُمْ وَرَبُّ ءَابَآئِكُمُ الاٌّوَّلِينَ ﴾
(La ilaha illa Huwa. He gives life and causes death -- your Lord and the Lord of your forefathers.) This is like the Ayah:
﴿قُلْ يَأَيُّهَا النَّاسُ إِنِّى رَسُولُ اللَّهِ إِلَيْكُمْ جَمِيعًا الَّذِى لَهُ مُلْكُ السَّمَـوَتِ وَالاٌّرْضِ لا إِلَـهَ إِلاَّ هُوَ يُحْىِ وَيُمِيتُ﴾
(Say: "O mankind! Verily, I am sent to you all as the Messenger of Allah -- to Whom belongs the dominion of the heavens and the earth. La ilaha illa Huwa. He gives life and causes death...) (7:158)