Musannaf Ibn Abi Shayba 21:436

Jarir narrated to us, from Mansur, from Abu Ishaq, from al-Agharr Abu Muslim, who testifies regarding Abu Hurayrah and Abu Sa'id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah grants respite until the first third of the night has passed, then He descends to the lowest heaven and says: 'Is there anyone seeking forgiveness? Is there anyone repenting? Is there anyone supplicating? Is there anyone asking?' until the dawn breaks."