Bilal bin Abdullah bin Unays narrates from his father, Sayyiduna Abdullah bin Unays (may Allah be pleased with him), that he said: O Messenger of Allah, tell me the night in which Laylat al-Qadr should be sought. He (peace and blessings be upon him) said: "Were it not for the fear that people would come for the prayer on that night only (and leave the other nights), I would certainly have told you; but seek it on the twenty-third night of the month."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13939