Sunan Abi Dawud, Hadith 1376 ⓘ
Narrated Ibn 'Abbas: The Prophet as saying: Seek laitat al-Qadr in the last ten night of Ramadan. When nine (nights) remain (i.e. on the twenty first), when seven (night) remain (i.e. on the twenty third), and when five (nights) remain (i.e. on the twenty fifth).
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا وُهَيْبٌ، أَخْبَرَنَا أَيُّوبُ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " الْتَمِسُوهَا فِي الْعَشْرِ الأَوَاخِرِ مِنْ رَمَضَانَ فِي تَاسِعَةٍ تَبْقَى وَفِي سَابِعَةٍ تَبْقَى وَفِي خَامِسَةٍ تَبْقَى " .
also referenced under: Hadith 1381 (DarusSalam) & Book 6, Hadith 1376 (USC-MSA)