What did Jesus Christ establish to be taught in the churches? What He brought - in what we consider to be the New Testament era - is not at all contradictory or fundamentally different from what the Old Testament teaches. His message is complementary, completing the teaching of the Old Testament, rounding out and finishing God's revelation to mankind.
The word "but" in verse 17 has been inserted by the translators. In those Bibles that use the convention, it is in italics, which shows that it is a word added by the translators to clarify what they believe is the sense. Why did they choose "but"? The translators' fundamental belief is that Jesus came to change what was taught by Moses. However, if they had put together what the rest of the New Testament says, Jesus came and added to and completed what Moses and the other prophets preached. There is a better word to insert there: "and." Thus, "For the law was given through Moses and grace and truth came through Jesus Christ." They are complementary, not contradictory. Perhaps the word "supplementary" would better explain it, though what Jesus brought is both complementary and supplementary.
"Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill" (Matthew 5:17). Consider a candy jar, which is filled only an inch. That represents what Moses taught, the law. But Jesus filled the rest of the candy jar full! Jesus brought the spirit of the law. He filled to the full the revelation of God.
What Moses taught in the law is the law of the Kingdom of God. It cannot be separated from the gospel of the Kingdom of God that Jesus brought because the Kingdom of God needs law to function. God's Kingdom is a real entity. It is designed to function, and it will only function through law and, of course, grace, as they work together.
Richard T. Ritenbaugh
Notice in verse 14 that Jesus is described as "full of grace"—suggesting lovingkindness and benevolent gifts—"and truth." Then, verse 16 says that from that fullness of grace we receive grace. In other words, it is from our relationship with Him that we receive many beneficent gifts toward salvation.
Other Bibles translate the phrase "grace for grace" as "grace on grace" or "grace upon grace." In a paraphrase, it may be rendered as "blessing after blessing." The phrase pictures grace as if it were objects being stacked one on top of another or endlessly linked as if side by side.
Our calling is an act of God's grace, a gifting completely apart from any merit on our part. We tend to think of grace primarily in regard to justification and the forgiveness of sin, but that is far, far too limiting. John is showing us that our relationship with God through Jesus Christ is a connection that supplies us with a continuous flow of grace, blessings, gifts, favor, powers, forgiveness, knowledge, understanding, wisdom, healings, protection, and more through God's loving concern.
He is not supplying our every desire but our every need as His spiritual creation of each of us moves toward His conclusion. Again, remember that, for this truth to be more fully appreciated, it must be understood that He does not owe us one tiny jot or tittle of it. Just as surely as the manna physically appeared to the unconverted Israelites every morning in the wilderness and the cloud was in the sky by day and a pillar of fire by night, God is supplying our every need in relation to His salvation and purpose.
It is all freely given toward His glorification and His purpose of creating us to fill a position, a place in His Kingdom. The apostles used charis ("grace") in many other situations, but they applied it most especially to mean the powers given by God to meet our spiritual needs.
John W. Ritenbaugh
Living By Faith and God's Grace
Jesus Christ was sent as the Forerunner (Hebrews 2:10, archegos, “one who goes before”) to live among men in order to reveal His Father, the Living God (Matthew 11:27; John 14:7-11; 17:6-7). This prodigious work necessitated that Christ be willing to “drink the cup” and suffer many burdens, the greatest being His arrest, persecution, crucifixion, and death at the hands of His own creation. As our Forerunner and an example to all men, it was incumbent on Christ to submit to the will of the Father and to do so with a perfect attitude of faithful humility. His incomparable level of submission allowed Him to become our Savior, a type of which is ultimately required of everyone to enter the Kingdom of God (Hebrews 11:6; James 4:6).
Martin G. Collins
The Miracles of Jesus Christ: Healing Malchus' Ear (Part Two)
This does not mean that what was in the law was not true. John is merely saying that grace came and a complete telling, or revealing, of the truth was made through the Mediator—Jesus Christ our Savior. He finished it, put the capstone on it, and revealed it to us.
So whatever does not agree with the truth is false or unprofitable. Whatever is false will not lead to eternal life but to the second death—where we do not want to go! Once we see that "the light of truth" has illuminated something false, we drop it. We should get away from it as fast as we can. Do not linger over it.
Richard T. Ritenbaugh