Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) came hurrying while we were sitting, and his haste alarmed us. When he (peace and blessings be upon him) reached us, he gave the greeting of peace and then said: "I came hurrying to you to tell you about Laylat al-Qadr (the Night of Decree), but between me and you (on the way) I was made to forget it, so seek it in the last ten nights."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12567