'Aishah (May Allah be pleased with her) reported:
The Messenger of Allah (ﷺ) used to seclude himself (in the mosque) during the last ten nights of Ramadan. He would say, "Search for Lailat-ul-Qadr (Night of Decree) in the last ten nights of Ramadan."[Al-Bukhari and Muslim].
App reference: Book 9, Hadith 201
Arabic/English book reference: Book 9, Hadith 1191