Sunan at-Tirmidhi (Jami-al-Tirmidhi), Chapter: Salah (Prayers)

that Allah's Messenger said, 'Allah, the Blessed and Exalted, comes down every night to the heaven of the earth when the first third of the night has passed away. He says: "I am the King. Who is it that will pray to Me that I may answer him? Who is it that will seek from Me that I may grant him? Who is it that will ask for My forgiveness that I may forgive him?" This ceases not till the brightness of dawn.' [Ahmed 7595, Bukhari 1145, Muslim 758, Abu Dawud 4314, Ibn e Majah 1366]