John Chrysostom

"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.