(40) باب فَضْلِ لَيْلَةِ الْقَدْرِ وَالْحَثِّ عَلَى طَلَبِهَا وَبَيَانِ مَحَلِّهَا وَأَرْجَى أَوْقَاتِ طَلَبِهَا
Ibn 'Umar (Allah be pleased with them) reported Allah's Apostle (ﷺ) as saying:
Seek Lailat-ul-Qadr in the last week (of Ramadan).
Reference: Sahih Muslim 1165 b
In-book reference: Book 13, Hadith 268
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2618