39 Do you wish to see how incapable he is of hurting you, unless permitted? “These,” he says, “wait all upon You, that You may give them meat in due season”. And this serpent wishes to devour, but he devours not whom he wishes....You have heard what the serpent's meat is. Thou dost not wish that God give you to be devoured by the serpent; because not the serpent's food: i.e. forsake not the Word of God. For where it is said to the serpent, “Dust you shall eat,” it is said to the transgressor, “Dust you are, and unto dust you shall return.” Thou dost not wish to be the serpent's food? Be not dust. How, you reply, shall I not be dust? If you have not a taste for earthly things. Hear the Apostle, that you may not be dust. For the body which you wear is earth: but do thou refuse to be earth. What means this? “Set your affection on things above, not on things on the earth.” If you dost not set your affections on earthly things, you are not earth: if you are not earth, you are not devoured by the serpent, whose appointed food is earth. The Lord gives the serpent his food when He will, what He will: but He judges rightly, he cannot be deceived, He gives him not gold for earth. “When You have given it them, they gather it.”...
40. “When you open Your hand, they shall all be filled with good”. What is it, O Lord, that You open Your hand? Christ is Your hand. “To whom is the arm of the Lord revealed?” To whom it is revealed, unto him it is opened: for revelation is opening. “When You open Your hand, they shall all be filled with good.” When Thou revealest Your Christ, “they shall all be filled with good.” But they have not good from themselves; this is oftentimes proved unto them. “When Thou hidest Your face, they are troubled”. Many filled with good have attributed to themselves what they had, and have wished to boast as in their own righteousnesses, and have said to themselves, I am righteous; I am great: and have become self-complacent. Unto these the Apostle speaks: “What have you, that you did not receive?” But God, wishing to prove unto man that whatever he has he has from Him, so that with good he may gain humility also, sometimes troubles him; He turns away His face from him, and he falls into temptation; and He shows him that his righteousness, and his walking aright, was only under His government....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)