The principle of agreement is the basic key to the kingdom of God. God made a covenant or agreement with man for his salvation. Jesus's atonement for sin is God's method to bring man into agreement with Himself so He can show His favor toward His men and women. The principle is that the place of agreement is the place of power.
Unbelief causes disagreement and disobedience. Belief brings agreement manifested in obedience. God's promise is that if we are in agreement with Him abiding in Him and His Word, then we can pray and God will hear and answer us. Further, that when any two believers agree on anything, God has promised to answer (Matt. 18:19).