The virtue of Lailat Al-Qadr and the Exhortation to seek it; When it is and the most likely times to seek it Sahih Muslim 1165 b
Arabic hadith text
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ، عُمَرَ - رضى الله عنهما - عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ "تَحَرَّوْا لَيْلَةَ الْقَدْرِ فِي السَّبْعِ الأَوَاخِرِ "
Translation
Ibn 'Umar (Allah be pleased with them) reported Allah's Apostle (ﷺ) as saying
Seek Lailat-ul-Qadr in the last week (of Ramadan).