There is only one prayer that anyone can pray with the assurance that God will hear him.  It is the prayer for mercy—mercy that possesses God’s forgiveness, restoration, and salvation.  It is the prayer of a humble heart that sincerely has decided to go God’s way.   Any other prayers that people utter, if they have not prayed this prayer (above), are an abomination to God and are not heard.  Why?  Well, it is not because God is not good.  He is good (Matt. 5:43-45).   It is because He cannot grant any other request of the unsaved, because they naturally do not do what is right or seek after God (Rom. 3:10-11).  Isaiah 64:6 tells us that all the unsaved are unclean and all their righteousness are like filthy rags to God.  Therefore, God will not listen to their prayers because all their requests are made with selfish, ungodly motives.