Sahih al-Bukhari Book 32, Hadith 9
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).
The Prophet (ﷺ) said, "Look for the Night of Qadr in the last ten nights of Ramadan ,' on the night when nine or seven or five nights remain out of the last ten nights of Ramadan (i.e. 21, 23, 25, respectively).
The Prophet (ﷺ) came out to inform us about the Night of Qadr but two Muslims were quarreling with each other. So, the Prophet (ﷺ) said, "I came out to inform you about the Night of Qadr but such-and-such persons were quarreling, so the news about it had been taken away; yet that might be for your own good, so search for it on the 29th, 27th and 25th (of Ramadan).