It is narrated from Sayyiduna Uthman bin Abi al-As al-Thaqafi (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The gates of the heaven are opened at midnight, and a caller calls out: Is there anyone supplicating, so that his supplication may be answered? Is there anyone asking, so that he may be given? Is there anyone in distress, so that his distress may be relieved? So no Muslim makes any supplication except that Allah answers it for him, except a fornicating woman who busies herself with her private parts (to earn from them), or a collector of tithes (an oppressive official)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8359