Introduction to Fiqh-us-Sunnah
The night of qadr is the most virtuous night of the year. Allah says in the Qur'an: "We revealed it on the night of power [that is, qadr]. What will tell you what the night of power is? It is better than a thousand months." Any action therein, for example, reciting the Qur'an, making remembrance of Allah, and so on, is better than acting for one thousand months which do not contain the night of qadr.
Volume 3, Page 145: Night of Qadr, it is preferred to seek this nightIt is preferred to seek this night during the last ten nights of Ramadan, as the Prophet, upon whom be peace, strove his best in seeking it during that time. We have already mentioned that the Prophet would stay up during the last ten nights, would wake his wives, and then would remain apart from them to worship.
Volume 3, Page 145a: Night of Qadr, which night is it?Scholars hold different opinions as to the night which is the night of qadr. Some are of the opinion that it is the 21st, some say the 23rd, others say the 25th and still others say it is the 29th. Some say that it varies from year to year but it is always among the last ten nights of Ramadan. Most scholars, though, vouch for the 27th.
Ahmad recorded, with a sahih chain, from Ibn 'Umar that the Prophet said: "He who likes to seek that night should do so on the 27th. Ubayy ibn K'ab said: By Allah, and there is no God but Him, it is during Ramadan--and He swore to that--and by Allah, I know what night it is. It is the night during which the Prophet ordered us to make prayers, the night of the 27th. Its sign is that the sun rises in the morning white and without any rays." This is related by Muslim, Abu Dawud, Ahmad, and by at-Tirmizhi who called it sahih.
Volume 3, Page 145b: Night of Qadr, praying and making supplications during the night of qadrAl-Bukhari and Muslim record from Abu Hurairah that the Prophet, upon whom be peace, said: "Whoever prays during the night of qadr with faith and hoping for its reward will have all of his previous sins forgiven."
As to the supplication during the night of qadr, 'Aishah said: "I asked the Messenger of Allah: 'O Messenger of Allah, if I know what night is the night of qadr, what should I say during it?' He said: 'Say: O Allah, You are pardoning and You love to pardon, so pardon me.' " This is related by Ahmad, Ibn Majah, and by atTirmizhi, who called it sahih.