Musnad Abu Ya'la al-Mawsili 155:315

Abu al-Rabi' narrated to us, Fulayh narrated to us, from al-Zuhri, from Abu Salamah ibn 'Abd al-Rahman and Abu 'Abd Allah al-Agharr, the companion of Abu Hurayrah, that they both heard Abu Hurayrah say: The Messenger of Allah (may Allah bless him and grant him peace) said: "Allah descends every night to the lowest heaven when the last third of the night remains, and He says: 'Who is complaining, that I may give to him? Who is calling upon Me, that I may answer him? Who is seeking forgiveness, that I may forgive him?'" For that reason, they used to prefer the prayer of the last part of the night over the first part of it.