Abdur Rahman narrates that once the mention of Laylat al-Qadr was made in the presence of Hazrat Abu Bakrah (may Allah be pleased with him), so he said: I will seek it only in the last ten nights because I heard something from the Prophet (peace and blessings be upon him) regarding it. I heard the Prophet (peace and blessings be upon him) say: Seek Laylat al-Qadr in the last ten nights of Ramadan—on the 21st, 23rd, 25th, or 27th night, or on the last night.
Hadith Referenceمسند احمد / أول مسند البصريين / 20404