It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that several Companions (may Allah be pleased with them) saw Laylat al-Qadr in their dreams during the last seven nights. So the Messenger of Allah (peace and blessings be upon him) said: "I see that your dreams are agreeing upon the last seven nights, so whoever among you is seeking this night should search for it in the last seven."
Hadith Referenceالسنن المأثورة / باب صيام من أصبح جنبا / 319
Hadith Takhrijصحیح بخاری، فضل ليلة القدر، باب التماس ليلة القدر في السبع الأواخر، رقم : 2015 ، صحیح مسلم، الصوم، باب فضل ليلة القدر والحث على طلبها، رقم: 1165