Qur'an

"They are those who spend a good portion of the night, prostrating themselves and standing before their Lord."

Qur'an 25:64

Hadith

"Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said, 'Our Lord Almighty descends to the lowest heaven in the last third of every night, saying: Who is calling upon Me that I may answer him? Who is asking from Me that I may give him? Who is seeking My forgiveness that I may forgive him?'"

Source: Sahih al-Bukhari 1145, Sahih Muslim 758