Prayer is Effective Because God Commands It
A Simple Command
In both the New and the Old Testament God commands his people to pray (Isa. 55:6, Matt. 7:7, Phil. 4:6, Eph. 6:18, 1 Thes. 5:17). Though people desired to pray, if God had not commanded it, there would be no way that it would be of any effect. If fact, if God had not commanded us to pray, it would be sin to do so. Because God is sovereign, he has the authority to command us to pray. A person would be foolish to think that God would respond in a positive way to them if they approached him in a way that he had not ascribed; far from being beneficial, it would be deadly (Lev. 10:1-2).
Prayer is commanded by God, and therefore is effective as a means for such things as to ask for temporal blessing (Gen. 28:20), to ask for spiritual blessing (Matt. 6:33), to ask for help in time of need (Heb. 4:16), to repent (1 Kgs. 8:33), and to praise God (Ps. 66:17). All these things we can do with confidence, knowing that God has commanded us to do them according to his sovereign plan and has provided us a way to approach him (Heb. 4:16).
A Command from a Sovereign God
Rather than speak to the question of how God, being sovereign can be influenced by the prayers of his people, if in fact he is influenced at all, there is a positive way to look at the fact that a sovereign God commands his people to pray. God is sovereign, and therefore because he commands his people to pray we can know that regardless of how, prayer is a means for God’s will to be accomplished on earth as it is in heaven (Matt. 6:10). Therefore, because the sovereign God of the whole universe, who is able to do all that we ask and abundantly more (Eph. 3:10), has commanded us to pray; let us pray all the more and with boldness!