"Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you. Let not your heart be troubled, neither let it be afraid." - John 14:27 KJV

The peace Jesus left for His disciples was reconciliation back to Himself. Only the “Son of God” - which is the flesh of God - could give this peace, because only God is without sin. God saw that there was no man that could be a Savior, so He robed Himself in flesh, came to earth to dwell among men, then gave His life on the cross to redeem man back to Himself.

"For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul." - Leviticus 17:11 KJV

"Ye have heard how I said unto you, I go away, and come again unto you. If ye loved me, ye would rejoice, because I said, I go unto the Father: for my Father is greater than I. [Perhaps speaking of His dwelling within the flesh temple of man compared to His dwelling filling the universe; perhaps also referring to accomplishing His mission as High Priest and Lamb to fulfill the Law of application of His blood in the Temple in heaven]" - John 14:28 KJV

The fulfillment of the peace Jesus gave is the Holy Ghost. Because Jesus paid the price of reconciliation by His blood, we are able to receive His Holy Spirit and become at one with God. No more separation because of sin – because of the blood that reconciled, we are reunited with God.]

"For it pleased the Father that in him should all fulness dwell; and, having made peace through the blood of his cross, by him to reconcile all things unto himself; by him, I say, whether they be things in earth, or things in heaven.

“And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight: If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;" - Colossians 1:19-23 KJV

What is the gospel that we have heard preached? The gospel is the death, burial, and resurrection of Jesus Christ. 1Corinthians 15:1-4.

How can we be presented holy, unblameable and unreproveable in His sight? By obedience to the gospel:

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. ... And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers." - Acts 2:38, 42 KJV