6 Let us now come to this verse of the Psalm: “The Lord is your defence upon the hand of your right hand”. By hand he means power. How do we prove this? Because the power of God also is styled the hand of God...Whereof John says, “He gave unto them power to become the sons of God.” Whence have you received this power? “To them,” he says, “that believe in His Name.” If then you believe, this very power is given you, to be among the sons of God. But to be among the sons of God, is to belong to the right hand. Your faith therefore is the hand of your right hand: that is, the power that is given you, to be among the sons of God, is the hand of your right hand...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)