Philippians 4:7

And never cast off the habit of reading in the Holy Scriptures; for nothing feeds the soul and enriches the mind so well as those sacred studies do. But look to this as the chief gain you are to make by them, that, in all due patience, ye may discharge the duties of your office religiously and piously—that is, in the love of Christ—and despise all transitory objects for the sake of His eternal promises, which in truth surpass all human comprehension and understanding, and shall conduct you into everlasting felicity.

When the peace of God has come upon us, we shall understand God. There will be no discord, no disagreement, no quarrelsome arguments, nothing subject to question. This is hardly the case in worldly life. But it shall be so when we have the peace of God, wherein all understanding shall be ours. For peace is the state of being already at rest, already secure.

"And the peace of God which passeth all understanding shall guard your hearts and your thoughts in Christ Jesus." What meaneth this? "The peace of God" which He hath wrought toward men, surpasseth all understanding. For who could have expected, who could have hoped, that such good things would have come? They exceed all man's understanding, not his speech alone. For His enemies, for those who hated Him, for those who determined to turn themselves away, for these, he refused not to deliver up His Only Begotten Son, that He might make peace with us. This peace then, i.e. the reconciliation, the love of God, shall guard your hearts and your thoughts.

For this is the part of a teacher, not only to exhort, but also to pray, and to assist by supplication, that they may neither be overwhelmed by temptations, nor carried about by deceit. As if he had said, May He who hath delivered you in such sort as mind cannot comprehend, may He Himself guard you, and secure you, so that you suffer no ill. Either he means this, or that that peace of which Christ saith, "Peace I leave with you, My peace I give unto you" (John xiv. 27): this shall guard you, for this peace exceedeth all man's understanding. How? When he tells us to be at peace with our enemies, with those who treat us unjustly, with those who are at war and enmity toward us; is it not beyond man's understanding? But rather let us look to the former. If the peace surpasseth all understanding, much more doth God Himself, who giveth peace, pass all understanding, not ours only, but also that of Angels, and the Powers above. What meaneth "in Christ Jesus"? Shall guard us in Him, so that ye may remain firm, and not fall from His faith.

That is, the peace which God established with mankind surpasses every mind, not only human but also angelic — as if the apostle said: He saved or delivered us in such a way that our mind is unable to comprehend it. For who expected that such blessings would be granted to us and that we would be reconciled with God? He Himself will guard and protect you, so that you would not even think anything evil. Or the apostle speaks of the peace of which the Lord said: "Peace I leave with you" (Jn. 14:27) — it will guard you. For such peace also surpasses every mind, since the Lord commands that we have peace with our enemies and with those who wrong us. And if the peace surpasses every mind, how much more the essence of the matter? The expression "in Christ Jesus" means: He keeps you in Himself, so that you would not fall away from Him, but rather abide in Him.

For the perfection of interior sanctity, there is necessarily required purity of conscience and tranquility of the whole soul through the peace of God surpassing all human understanding.

In the beginning I call upon the first principle, from whom all illuminations descend as from the Father of lights, from whom is every good gift and every perfect gift, namely the eternal Father, through his Son, our Lord Jesus Christ, that by the intercession of the most holy Virgin Mary, mother of the same God and our Lord Jesus Christ, and of blessed Francis, our leader and father, he may give the enlightened eyes of our mind to direct our feet in the way of that peace which surpasses all understanding; which peace our Lord Jesus Christ proclaimed and gave.

Then when he says, and the peace of God... will keep your hearts, he asks that peace descend on the soul now instructed by the things said above. He asks this as though he were entreating. Peace, according to Augustine, is the tranquility of order: for the disturbance of order is the destruction of peace. This tranquility of order is considered from three aspects: first, insofar as it exists in the principle of order, namely, in God: "For there is no authority except from God, and those that exist have been instituted by God. Therefore he who resists the authorities resists what God has appointed" (Rom. 13:1). From that profound source in which peace exists it flows first into the beatified, in whom there is no disturbance either of guilt or of punishment; then it flows into saintly men: the holier he is, the less his mind is disturbed: "Great peace have those who love thy law" (Ps. 119:165). But it is more perfect in the beatified: "Behold, I will extend prosperity to her like a river, and the wealth of the nations like an overflowing stream" (Is. 66:12). Now because God alone can deliver the heart from all disturbance, it is necessary that it come from Him; hence he says, of God: and this, inasmuch as peace considered in that source passes all created understanding, as it is stated in 1 Timothy (6:16): "Who alone dwells in unapproachable light"; "Behold, God is great, and we know him not; the number of his years is unsearchable" (Job 36:26). As it exists in heaven, it surpasses all the knowledge of the angels; but as it exists in the saints on earth, it surpasses all the knowledge of those who lack grace: "To him who conquers I will give some of the hidden manna, and I will give him a white stone" (Rev. 2:17).

And the peace, therefore, will keep your hearts, i.e., your affections, so that you will never depart from the good in anything: "Keep your heart with all vigilance; for from it flow the springs of life" (Prov. 4:23); and your minds, so that they not deviate from the truth in anything. And this, in Christ Jesus, by whose love your affections are kept from evil and by whose faith your mind continues in the truth.