A Covenant Is Not a Testament
He took bread. Then He took the cup. He gave thanks for it, and said it was the new covenant in his blood. In other words, the cup symbolizes the new covenant, a covenant His death put in force. The old, Mosaic Covenant, the one the Scripture summarizes as the Ten Commandments (Exodus 34:28), was put in force by the blood of young bulls (Exodus 24:5-8). Moses took the blood, sprinkled it on the altar, read the words of the covenant to the people, and, after a pledge of obedience by the people, he sprinkled the people. “Behold the blood of the covenant, which the Lord has made with you in accordance with all these words,” he said.
So, blood establishes a covenant. “A covenant is not a testament,” Robertson writes. “A covenant is a bond in blood. It involves commitments with life and death consequences. At the point of covenantal inauguration, the parties of the covenant are committed to one another by a formalizing process of blood-shedding. This blood-shedding represents the intensity of the commitment of the covenant.”
So, the question is: “What commitments, what covenantal promises did God make that Christ inaugurated by His blood shedding?” And therefore, when we drink the cup, what promises are we ‘drinking’ by faith? This is big. Jeremiah 31:31-34 speaks of this new covenant. I’ll simply read that passage from the ESV and insert some observations.
The New Covenant
31 “Behold, the days are coming, declares the Lord, when I will make a new covenant with the house of Israel and the house of Judah, 32 not like the covenant that I made with their fathers on the day when I took them by the hand to bring them out of the land of Egypt, my covenant that they broke, though I was their husband, declares the Lord.”
Observation #1-The new covenant is not like the old. Therefore, the new is not a newer version of the old. It’s not a renewed edition of the old. Nor is it, as some put it, a new administration of the old. It’s, as Scripture puts it, not like the old. It’s new. It’s simple. But take my word for it: many, even those we would respect, do not understand. The new is not like the old. Therefore, the old is not continued in the new. There is absolute discontinuity between the old and new covenants, in other words.
33 But this is the covenant that I will make with the house of Israel after those days, declares the Lord: I will put my law within them, and I will write it on their hearts.”
Observation #2- God promises, in the new covenant, to write his law within, on the hearts of his people. The Old Covenant Law was written on tablets of stone. It was exterior. It commanded from without, much like a guardian or a super nanny. And as the history of the Old Covenant people shows, it had no real effect. It did not produce what it called for. “My people are bent on turning from Me,” the Lord says in Hosea. His people were bent on turning from him. Therein lies the heart of the issue. Law, external law, does not change the heart of a sinner.
But in the new covenant, God makes that which is external, internal. What is exterior, he makes interior. His precise words are fascinating. He says that he will put his “law within them,” and “will write it on their hearts.” The question is “What law?” What law does he promise to put within? Some (many!) say without hesitation that God here promises to inscribe the Ten Commandments upon the hearts of his people. Maybe, but I doubt it. I doubt it for a number reasons, among which are:
(1) Scripture speaks about the Mosaic Law as an integral whole. It’s always all or nothing. Therefore, the entire law, not just part of it (like The Ten Commandments), would be in view. I know of no one who claims that much.
(2) Paul statement in Galatians 3:19 makes clear that the Law covenant was a provisional, temporary thing. He says “Why then the law? It was added because of transgressions, untilthe offspring should come to whom the promise had been made (i.e. Christ)…”To write on the human heart that which came to an end when Christ came is absurd. Why would God do that? I don’t think he would. That would be at odds with Scripture and thus fly in God’s own face.
(3) Paul’s statement in Colossians 2:16 and 17 convinces me where to look for the answer and therefore how to understand Jeremiah. Paul writes: “…let no one act as your judge in regard to food or drink (so matters of diet) or in respect to a festival or new moon (sounds like ceremony) or a Sabbath day (which is one of the Ten) – (17) things which are a mere shadow of what is to come; but the substance belongs to Christ.” What injustice is done to Christ, or what twisting of Scripture is performed, by saying the entire Mosaic Law, including the Ten Commandments, is but a mere shadow of the Son of God? Is this not a truly glorious thing!
When God said he would write his law on the hearts of all in the new covenant, I am more than convinced he meant the law of Christ, that is, the law who is Christ. God has sent forth the Spirit of His Son into the hearts of believers (Gal. 4:6). Writes one:
“The Law was an … incomplete expression of God’s moral will that by definition faded into oblivion when the … complete expression of God’s moral will filled up all that the Law was ever intended to be” (CR Bresson, NCT & The Enfleshment of the Law).
God does write his law on the hearts of his NC people. And that Law is Christ.
Moving on in verse 33:
And I will be their God, and they shall be my people. 34 And no longer shall each one teach his neighbor and each his brother, saying, ‘Know the Lord,’ for they shall all know me, from the least of them to the greatest, declares the Lord. For I will forgive their iniquity, and I will remember their sin no more.” 
Observation #3- Unlike the old covenant, everyone under the new are believers. Everyone in the new covenant is converted. They know the Lord in a saving way; there is no forgiveness apart from faith. And God promises to forgive their sins in full. This is why we’re a Baptist church and not, for example, a Presbyterian, big “R” Reformed church that baptizes babies into ‘the covenant.’ Why not make our tent bigger and just be Sovereign Grace Church? This is why. If it isn’t true, then we might as well go home. But if it is, then we must stand, despite how small we get.
So, the cup that we drink represents this new covenant in Christ’s blood. Which means that by His death, Christ secured, or purchased, and put in force or inaugurated, these promises. God promised to write his law on the heart: exterior law does not secure obedience. But the law of Christ written on the heart does. Just think it through: The fruit of the spirit of Christ who is the Holy Spirit is … This is cause for unspeakable comfort and encouragement. God has promised with a bond in Christ’s blood, His own blood, to make his own obedient. Because Christ by His Spirit is in us, we can live holy and godly lives. Robertson, Christ of the Covenants, pp. 14-15.
 The Holy Bible : ESV. 2001 (Ga 3:19). Wheaton: Standard Bible Society.
 The Holy Bible : English standard version. 2001 (Je 31:31–34). Wheaton: Standard Bible Society.
Todd Braye serves as pastor for Sovereign Grace Baptist Church, Blackie, AB