The Qadr Night

Sacred nights are esteemed by Islam. Having great mercy upon His slaves, Allâhu ta'âlâ has made some nights valuable and has declared that He will accept the prayers and istighfârs done on these nights. He has made these nights opportunities for His slaves to worship much, to pray and ask for forgiveness. A sacred night is named after the day following it. It is the duration of time from the early afternoon prayer of the preceding daytime till the dawn following the night. Only, the night of Arafa and the three nights of Qurbân are not so. These four nights follow the daytime after which they are named. We must benefit from these nights, perform our omitted prayers of namâz, read the Qur'ân, say prayers and istighfâr, give alms, please Muslims and send the thawâb to the souls of the dead, too. We must respect these nights. To respect them means not to commit sins during them.
It is written on the hundred and seventy-second page of the book Riyâd-un-nâsihîn, "Imâm-i Nawawî says in his book Azkâr, 'To utilize one-twelfth of the night [about one hour] means to utilize the whole night. This is the case for summer and winter nights alike.' [Ibni Âbidîn gives detailed information on this subject, on the four hundred and sixty-first page of the first volume and on the two hundred and eighty-ninth page of the third volume.] It is written in Haqâyiq-i manzûma, 'In books of fiqh, an hour means an amount of time.' Imâm-i Nawawî is a mujtahid in the Shâfi'î Madhhab. It is good also for those who are Hanafî to benefit from the nights in this manner."
QADR NIGHT is a night in the blessed month of Ramadân. Imâm-i a'zam Abû Hanîfa said that the most probable night was the twenty-seventh. We have been told to look for it between the twentieth and the thirtieth nights. It is the most valuable night praised in the Qur'ân. The Qur'ân began to be revealed to Rasûlullah on this night. [Endless Bliss, 3rd Fascicle]