Musnad Abu Ya'la al-Mawsili 152:251

Abu Khaythama narrated to us, Abd al-Samad ibn Abd al-Warith narrated to us, Abd al-Aziz ibn Muslim narrated to us, Abu Ishaq narrated to us, from Abu al-Ahwas, from Ibn Mas'ud, that the Messenger of Allah (may Allah bless him and grant him peace) said: "When the remaining third of the night is left, Allah descends to the lowest heaven. Then the gates of heaven are opened, then they are spread out, then He says: 'Is there any petitioner?' And He continues like that until the dawn rises."