3 “Peace,” He said, “I leave with you, my peace I give unto you.” It is here we read in the prophet, “Peace upon peace:” peace He leaves with us when going away, His own peace He will give us when He comes in the end. Peace He leaves with us in this world, His own peace He will give us in the world to come. His own peace He leaves with us, and abiding therein we conquer the enemy. His own peace He will give us when, with no more enemies to fight, we shall reign as kings.
Peace He leaves with us, that here also we may love one another: His own peace will He give us, where we shall be beyond the possibility of dissension. Peace He leaves with us, that we may not judge one another of what is secret to each, while here on earth: His own peace will He give us, when He “will make manifest the counsels of the heart; and then shall every man have praise of God.” And yet in Him and from Him it is that we have peace, whether that which He leaves with us when going to the Father, or that which He will give us when we ourselves are brought by Him to the Father.
And what is it He leaves with us, when ascending from us, save His own presence, which He never withdraws? For He Himself is our peace who has made both one. It is He, therefore, that becomes our peace, both when we believe that He is, and when we see Him as He is. For if, so long as we are in this corruptible body that burdens the soul, and are walking by faith, not by sight, He forsakes not those who are sojourning at a distance from Himself; how much more, when we have attained to that sight, shall He fill us with Himself?
Source: Tractates on the Gospel of John (New Advent)