From Sahih Bukhari (Hadith 2022):
Narrated Ibn `Abbas:Allah's Messenger (ﷺ) said, "The Night of Qadr is in the last ten nights of the month (Ramadan), either on the first nine or in the last (remaining) seven nights (of Ramadan)." Ibn `Abbas added, "Search for it on the twenty-fourth (of Ramadan)
Reference: Bukhari 2022