Philippians 4:7

7.And the peace of God Some, by turning the future tense into the optative mood, convert this statement into a prayer, but it is without proper foundation. For it is a promise in which he points out the advantage of a firm confidence in God, and invocation of him. “If you do that,” says he, “the peace of God will keep your minds and hearts.” Scripture is accustomed to divide the soul of man, as to its frailties, into two parts — the mind and the heart. The mind means the understanding, while the heart denotes all the disposition or inclinations. These two terms, therefore, include the entire soul, in this sense, — “The peace of God will guard you, so as to prevent you from turning back from God in wicked thoughts or desires.”

It is on good ground that he calls it the peace of God, inasmuch as it does not depend on the present aspect of things, (238) and does not bend itself to the various shiftings of the world, (239) but is founded on the firm and immutable word of God. It is on good grounds, also, that he speaks of it as surpassing all understanding or perception, for nothing is more foreign to the human mind, than in the depth of despair to exercise, nevertheless, a feeling of hope, in the depth of poverty to see opulence, and in the depth of weakness to keep from giving way, and, in fine, to promise ourselves that nothing will be wanting to us when we are left destitute of all things; and all this in the grace of God alone, which is not itself known otherwise than through the word, and the inward earnest of the Spirit.