Tafsir of Al-Qadr 97:3

And what will make you know what the Night of Al-Qadr is? The Night of Al-Qadr is better than a thousand months. Imam Ahmad recorded that Abu Hurayrah "When Ramadan would come, the Messenger of Allah would say,

قد جاءكم شهر رمضان شهر مبارك افترض الله عليكم صيامه

تفتح فيه أبواب الجنة وتغلق فيه أبواب الجحيم وتغل فيه الشياطين

فيه ليلة خير من ألف شهر من حرم خيرها فقد حرم

Verily, the month of Ramadan has come to you all. It is a blessed month, which Allah has obligated you all to fast. During it the gates of Paradise are opened, the gates of Hell are closed and the devils are shackled. In it there is a night that is better than one thousand months. Whoever is deprived of its good, then he has truly been deprived.'' An-Nasa'i recorded this same Hadith. Aside from the fact that worship during the Night of Al-Qadr is equivalent to worship performed for a period of one thousand months, it is also confirmed in the Two Sahihs from Abu Hurayrah that the Messenger of Allah said,

من قام ليلة القدر إيمانا واحتسابا غفر له ما تقدم من ذنبه

Whoever stands (in prayer) during the Night of Al-Qadr with faith and expecting reward (from Allah), he will be forgiven for his previous sins. The Descent of the Angels and the Decree for Every Good during the Night of Al-Qadr Allah says,

تنزل المﻼيكة والروح فيها بٳذن ربهم من كل أمر