On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Messenger of Allah (Sal Allahau Alaihi Wa Aalihi Wasallam) said:
Our Lord (Glorified and Exalted be He) descends each night to the earth’s sky when there remained 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 at-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.