The Messenger of Allah (peace be upon him) said : “Our Lord (glorified and exalted be He) descends each night to the earth’s sky when there remains the final third of the night, and He says: Who is saying a prayer to Me that I may answer it? Who is asking something of Me that I may give it him? Who is asking forgiveness of Me that I may forgive him?”
It was related by al-Bukhari (also by Muslim, Malik, at-Tirmidhi and Abu Dawud). In a version by Muslim the Hadith ends with the words : And thus He continues till [the light of] dawn shines.