Sunan at-Tirmithiy كتاب الصوم باب ما جاء فى ليلة القدر

حَدَّثَنَا حُمَيْدُ بْنُ مَسْعَدَةَ حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ حَدَّثَنَا عُيَيْنَةُ بْنُ عَبْدِ الرَّحْمَن ِقَالَ حَدَّثَنِى أَبِى قَالَ ذُكِرَتْ لَيْلَةُ الْقَدْرِ عِنْدَ أَبِى بَكْرَةَ فَقَالَ مَا أَنَا بِمُلْتَمِسِهَا لِشَىْءٍ سَمِعْتُهُ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم إِلاَّ فِى الْعَشْرِ الأَوَاخِرِ فَإِنِّى سَمِعْتُهُ يَقُولُ الْتَمِسُوهَا فِى تِسْعٍ يَبْقَيْنَ أَوْ فِى سَبْعٍ يَبْقَيْنَ أَوْ فِى خَمْسٍ يَبْقَيْنَ أَوْ فِى ثَلاَثٍ أَوْ آخِرِ لَيْلَةٍ. قَالَ وَكَانَ أَبُو بَكْرَةَ يُصَلِّى فِى الْعِشْرِينَ مِنْ رَمَضَانَ كَصَلاَتِهِ فِى سَائِرِ السَّنَةِ فَإِذَا دَخَلَ الْعَشْرُ اجْتَهَدَ. قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ.
The Glorious Night of Determination (1) was mentioned in the presence of Abū-Bakrah who said, "I only seek it in the last ten nights [of Ramaḍan] as I heard the Messenger of God, peace and blessings of God be upon him, say, 'Seek it when there remains nine nights, when there remains seven nights, when there remains five nights, when there remains three nights or on the last night.'" Abū-Bakrah used to pray during the first twenty nights of Ramaḍān the same way he would during the rest of the year, but would strive [in his worship] in the last ten days.
(1) The night during which the Qur'ān was first revealed to prophet Muhammad. It occurs on one of the last ten nights of Ramaḍān, although God only knows which night. The Qur'ān states that on this night, God determines the course of the world and all human affairs for the coming year. (2) Some interpretations state that it can be sought on the even numbered nights, as well.