‘One is said to be helped by another in two ways; in one way, inasmuch as he receives power from him: and to be helped thus belongs to the weak; but this cannot be said of God, and thus we are to understand, “Who hath helped the Spirit of the Lord?” In another way one is said to be helped by a person through whom he carries out his work, as a master through a servant. In this way God is helped by us; inasmuch as we execute His orders, according to 1 Corinthians 3:9: “We are God’s co-adjutors.” Nor is this on account of any defect in the power of God, but because He employs intermediary causes, in order that the beauty of order may be preserved in the universe; and also that He may communicate to creatures the dignity of causality.’
Summa Theologica, I.I., Q. 23, Art. 8.