Ziyad related to me from Malik that he had heard a man he trustedof the people of knowledge say, "The Messenger of Allah, may Allahbless him and grant him peace, was shown the lifespans of the people(who had gone) before him, or what Allah willed of that, and it was asif the lives of the people of his community had become too short forthem to be able to do as many good actions as others before them hadbeen able to do with their long lives, so Allah gave him Laylat al-Qadr, which is better than a thousand months."
USC-MSA web (English) reference: Book 19, Hadith 16
Arabic reference: Book 19, Hadith 706