Narrated Abu Huraira:
Allah’s Apostle said, “When it is the last third of the night, our Lord, the Blessed, the Superior, descends every night to the heaven of the world and says, ‘Is there anyone who invokes Me (demand anything from Me), that I may respond to his invocation; Is there anyone who asks Me for something that I may give (it to) him; Is there anyone who asks My forgiveness that I may forgive him?’ ”
Sahih Bukhari, Volume 8, Book75, Number 333