Musnad Abu Ya'la al-Mawsili 246:18

Zuhayr narrated to us, Hisham ibn Abd al-Malik narrated to us, Hammad ibn Salamah narrated to us, from Amr ibn Dinar, from Nafi ibn Jubayr ibn Mut'im, from his father, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Allah, the Exalted and Majestic, descends to the lowest heaven every night and says: 'Is there any supplicant so that I may answer him? Is there any seeker of forgiveness so that I may forgive him?'"