975. Narrated Ibn Abbas (R.A.A.) The Prophet (S.A.W.) 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. 21st, 23rd, 25th, (27th, 29th) respectively].”
(Bukhari: Book # 33, Chapter # 32, Hadith # 975)
1223. Ayesha (R.A.A.) reported: When the last ten nights (of Ramadan) would begin, the Messenger of Allah (S.A.W.) would keep awake at night (for prayer and devotion), awaken his family and prepare himself to be more diligent in worship.
(Bukhari and Muslim: Riyadh-us-Saliheen, Hadith # 1223)
1189. Abu Hurairah (R.A.A.) reported: The Prophet (S.A.W.) said, "Whosoever performs Qiyam during Lailat-ul-Qadr (Night of Decree), with Faith and being hopeful of Allah's reward, will have his former sins forgiven.''
(Bukhari and Muslim: Riyadh-us-Saliheen, Hadith # 1189)