(40) باب فَضْلِ لَيْلَةِ الْقَدْرِ وَالْحَثِّ عَلَى طَلَبِهَا وَبَيَانِ مَحَلِّهَا وَأَرْجَى أَوْقَاتِ طَلَبِهَا
'A'isha (Allah be pleased with her) and Ibn Numair reported Allah's Messenger (ﷺ) as saying:
Look for (and in the words of Waki, seek) Lailat-ul-Qadr in the last ten nights of Ramadan.
Reference: Sahih Muslim 1169
In-book reference: Book 13, Hadith 282
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2632