4 But why is it that, when He said, “Peace I leave with you,” He did not add, “my;” but when He said, “I give unto you,” He there made use of it? Is “my” to be understood even where it is not expressed, on the ground that what is expressed once may have a reference to both? Or may it not be that here also we have some underlying truth that has to be asked and sought for, and opened up to those who knock thereat? For what, if by His own peace He meant such to be understood as that which He possesses Himself?
Whereas the peace, which He leaves us in this world, may more properly be termed our peace than His. For He, who is altogether without sin, has no elements of discord in Himself; while the peace we possess, meanwhile, is such that in the midst of it we have still to be saying, “Forgive us our debts.” A certain kind of peace, accordingly, we do possess, inasmuch as we delight in the law of God after the inward man: but it is not a full peace, for we see another law in our members warring against the law of our mind. In the same way we have peace in our relations with one another, just because, in mutually loving, we have a mutual confidence in one another: but no more is such a peace as that complete, for we see not the thoughts of one another's hearts; and we have severally better or worse opinions in certain respects of one another than is warranted by the reality.
And so that peace, although left us by Him, is our peace: for were it not from Him, we should not be possessing it, such as it is; but such is not the peace He has Himself. And if we keep what we received to the end, then such as He has shall we have, when we shall have no elements of discord of our own, and we shall have no secrets hid from one another in our hearts. But I am not ignorant that these words of the Lord may be taken so as to seem only a repetition of the same idea, “Peace I leave with you, my peace I give unto you:” so that after saying “peace,” He only repeated it in saying “my peace;” and what He had meant in saying “I leave with you,” He simply repeated in saying “I give unto you.”
Let each one understand it as he pleases; but it is my delight, as I believe it is yours also, my beloved brethren, to keep such hold of that peace here, where our hearts are making common cause against the adversary, that we may be ever longing for the peace which there will be no adversary to disturb.
Source: Tractates on the Gospel of John (New Advent)