When it comes to the new covenant promise in Jeremiah 31:31-40, there are four questions that we should ask about the text. First, Who is the New Covenant between?
The passage itself identifies the two “parties” of the contract, multiple times, and the context of the entire chapter and book leave no doubt.
Jeremiah prophesied about both the destruction and rebuilding of Jerusalem. Chapter 31 comes after fourteen messages of condemnation on Judah’s idolatry, apostasy, and moral decay. Jeremiah’s people, the Jews, had been rebelling against God, and God is predicting two things for them: judgment and then salvation. The two parties are, therefore, 1) the LORD and 2) Israel.
Verse 31: “the days are coming, declares the LORD, when I will make a new covenant with the house of Israel and the house of Judah.” The nation was divided at this point in their history into the northern and southern kingdoms. Yet Israel and Judah were still family. They are the ones descended from “their fathers” (verse 32). Which fathers? The ones that the LORD brought out of the land of Egypt, the sons of Jacob—the Twelve Tribes of Israel (the rest of verse 32).
To that growing group the LORD gave laws, also called the Mosaic covenant, summarized in the Ten Commandments. In the desert, and also once they began to occupy parts of the Promised Land, Israel disobeyed those laws. Would God move on to another people? No. “This is the covenant that I will make with the house of Israel” (verse 33). They did not obey, their hearts were hard against Him, and this new covenant promises to get to the root of the problem. The LORD said, “I will put my law within them, and I will write it on their hearts” (verse 33).
After He finished making the promise, the LORD made a comparison about what it would take for these promises not to take place. We’ll look at those specifics shortly, but verses 35-37 repeat the parties: “Thus says the LORD,” “the LORD of hosts” (verse 35), “declares the LORD,” “the offspring of Israel being a nation,” (verse 36), and again, “says the LORD,” “all the offspring of Israel,” “declares the LORD” (verse 37).
The parallel passage in Ezekiel 36 is just as clear, and perhaps even more so as it distinguishes the “house of Israel“ (verses 22, 32, 37) from “among the nations” (verses 22, 23, 24, 30, and 36). There are three groups: the LORD, His chosen nation Israel, and all the other nations. The new covenant that the LORD made is not with any of the other nations than Israel.
It makes a Bible-reader wonder, as just one example, about the following note in the ESV Study Bible: “Do the terms in Jer. 31:27, 31, 36-37 focus the prophecy on ethnic Israel or on a redefined Israel (the Jewish-Gentile church)?” (page 1431, emphasis mine). Where is the warrant to redefine “Israel”? Would an Israelite accept such redefinition of terms?