Some men amongst the companions of the Prophet (ﷺ) were shown in their dreams that the night of Qadr was in the last seven nights of Ramadan. Allah's Messenger (ﷺ) said, "It seems that all your dreams agree that (the Night of Qadr) is in the last seven nights, and whoever wants to search for it (i.e. the Night of Qadr) should search in the last seven (nights of Ramadan).
Sahih al-Bukhari Book 32, Hadith 2
← Previous Hadith The Prophet (ﷺ) said, "Whoever fasted the month of Ramadan out of sincere Faith (i.e. belief) and hoping for a reward from Allah, then all his past sins will be forgiven, and whoever stood for the prayers in the night of Qadr out of sincere Faith and hoping for a reward from Allah, then all his previous sins will be forgiven ."

Sahih al-Bukhari Book 32, Hadith 1 Next Hadith → I asked Abu Sa`id, and he was a friend of mine, (about the Night of Qadr) and he said, "We practiced I`tikaf (seclusion in the mosque) in the middle third of the month of Ramadan with the Prophet (ﷺ) . In the morning of the 20th of Ramadan, the Prophet (ﷺ) came and addressed us and said, 'I was informed of (the date of the Night of Qadr) but I was caused to forget it; so search for it in the odd nights of the last ten nights of the month of Ramadan. (In the dream) I saw myself prostrating in mud and water (as a sign). So, whoever was in I`tikaf with me should return to it with me (for another 10-day's period)', and we returned. At that time there was no sign of clouds in the sky but suddenly a cloud came and it rained till rainwater started leaking through the roof of the mosque which was made of date-palm leaf stalks. Then the prayer was established and I saw Allah's Messenger (ﷺ) prostrating in mud and water and I saw the traces of mud on his forehead."

Sahih al-Bukhari Book 32, Hadith 3