Paul saith, 'Not of works, lest any man should boast.' Now, faith excludes all boasting. The hand which receives charity does not say, 'I am to be thanked for accepting the gift'; that would be absurd. When the hand conveys bread to the mouth it does not say to the body, 'Thank me; for I feed you.' It is a very simple thing that the hand does though a very necessary thing; and it never arrogates glory to itself for what it does. So God has selected faith to receive the unspeakable gift of His grace, because it cannot take to itself any credit, but must adore the gracious God who is the giver of all good.
The Lord gave the wonderful promise of the free use of His Name with the Father in conjunction with doing His works. The disciple who lives only for Jesus' work and Kingdom, for His will and honor, will be given the power to appropriate the promise. Anyone grasping the promise only when he wants something very special for himself will be disappointed, because he is making Jesus the servant of his own comfort. But whoever wants to pray the effective prayer of faith because he needs it for the work of the Master will learn it, because he has made himself the servant of his Lord's interests.