1) God WILL do nothing in answer to prayer, because He has already pre-ordained the whole outcome of history, down to the smallest incident. For God to actually respond to prayer would mean that He is dependent on man and that man can have an influence on God – if that were the case, God could not truly be sovereign. At best prayer is merely finding and professing agreement with the things God has already determined.
2) God CAN do nothing without prayer, because He has no jurisdiction on earth so needs mankind’s prayer to give Him authority to act here. After creating man, God gave man authority on earth – something that man soon gave over to Satan through Adam and Eve’s disobedience. Jesus as man won back that authority for man, enabling God legal access to act on earth again through the intercession of men and women.
3) God has chosen to respond to prayer. Prayer is not some kind of force independent of the one to whom we pray. God doesn’t NEED mankind to pray but mankind needs to pray to Him. God has established prayer as a way for man to grow in relationship with Him. Prayer can test faith, and faith exercised strengthens the relationship between man and God. Prayer encourages us into a greater understanding of who God is and what His purposes are.
God WILL change things in the world and in people’s lives in response to prayer, if a variety of conditions are met such as: faith, the right motive; and right relationship with God and with others. A requested outcome has to be in accordance with God’s character and His greater purposes.
I refer to character and purposes instead of saying “according to God’s will” because many people pick up strange ideas about God’s will from isolated bible verses, or from teachings they adopt and many see that “God’s will” is something fixed, predetermined and unchangeable and yet through scripture we see multiple instances of God changing His intended action in response to prayer and/or repentance.