It is narrated from Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Indeed Allah, the Mighty and Majestic, descends to the lowest heaven every night and says: Is there anyone supplicating, that I may answer him? Is there anyone seeking forgiveness, that I may forgive him?"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8341