Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: I was asleep when (someone) came to me, and it was said to me: Tonight is Laylat al-Qadr. So I got up while drowsy, and my feet got caught in some of the ropes of the tent of the Messenger of Allah (peace and blessings be upon him). Then I came to the Prophet (peace and blessings be upon him) while he was standing in prayer. Ibn Abbas (may Allah be pleased with them both) said: I looked into that night, and it was the twenty-third night.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11727