Jesus is the reason that the Sinai covenant and the Last Supper covenant can share the same DNA and yet be two different covenants—the historical old covenant and the historical new covenant. History itself is now divided into categories of BC and AD because Jesus came in history, and His covenant can be thought of that way also.
His coming made the old ritual system (including, for example, circumcision and animal sacrifices) obsolete. At the same time, it initiated a new ritual system (including baptism and the Lord’s Supper).
Regarding the commandment “that we love one another” (2 John 5), John could say, “I write no new commandment to you, but an old commandment which you have had from the beginning,” and yet “a new commandment I write to you, which thing is true in Him and in you” (1 John 2:7, 8, NKJV). How could John say that “love one another” was “no new commandment,” and yet it was “a new commandment”? Because, once we saw the command to “love one another” lived out in Jesus’ life, it became “new.” The same commandment was both “old” and “new” after Jesus came in the middle.
Similarly, the divine covenant through which God had broadcast His gospel and invited all who heard it to participate in it became a “new covenant” once He came to earth in the flesh. We saw the promises that make up its essential DNA being fulfilled in His life. Equally important, if not more so, the once-for-all sacrifice of His shed “blood of the everlasting covenant” (Heb. 13:20) simultaneously brought an end to animal sacrifices (8:13) and instituted the Lord’s Supper. At the DNA level, it remained the same covenant, but there had been a transformation historically.
What was true on the historical plane is also true on the experiential. An old-covenant experience becomes a new-covenant experience when Jesus comes into the middle. One’s response to His universal and timeless appeal, “Turn to Me, and be saved, all the ends of the earth” (Isa. 45:22, NASB), determines whether they live an old-covenant experience with no eternal hope or a new-covenant experience destined to “inherit the kingdom prepared for you from the foundation of the world” (Matt. 25:34).
The people at Sinai told Moses, “Tell us all that the Lord our God says to you, and we will hear and do it,” to which Jesus responded hauntingly, with aching heart: “Oh, that they had such a heart in them that they would fear Me and always keep all My commandments, that it might be well with them and with their children forever!” (Deut. 5:27–29, NKJV). He knew the severity of the temptations and discouragements yet to come. He knew that without His constant presence in their lives they would fail.
He wanted them to know how deeply He loved them and the depth of commitment He had made to them. In the Shema, He assured them: “These words which I command you today shall be in your heart” (6:6, NKJV). That assurance was both an invitation and a promise. It invited them to seek Him daily and promised them that He would write His law in their hearts, transforming His every command into a promise of what He would accomplish for them and in them. He gives that same assurance to us.