From Sahih Muslim (Hadith 1773):
Abu Huraira reported Allah's Messenger (ﷺ) as saying:Allah descends every night to the lowest heaven when one-third of the first part of the night is over and says: I am the Lord; I am the Lord: who is there to supplicate Me so that I answer him? Who is there to beg of Me so that I grant him? Who is there to beg forgiveness from Me so that I forgive him? He continues like this till the day breaks
Reference: Muslim 1773