In this series of questions about Jeremiah 31:31-40, here is the third: What guarantees the New Covenant? Or, on whom does the New Covenant depend?
Covenants are often distinguished between those that are conditional, “If you do this, then I’ll do this,” and those that are unconditional, “I will do this no matter what.” God’s covenant with Abram in Genesis 15, when God put Abram to sleep and walked between the dead animal halves alone, showed God’s commitment to act for Himself. Abram participated by receiving, not by contributing. It is the same sort of language in Jeremiah 31 and Ezekiel 36.
The guarantee of these promises is the word of the LORD. He has said it, and He has said it for His own sake. He has also confirmed the likelihood of His completing the promises by comparing them to “this fixed order.”
The new hearts and the fruitful land for the house of Israel are as certain as planets in orbit and the ocean tide. “If this fixed order departs from me, declares the LORD, then shall the offspring of Israel cease from being a nation before me forever” (Jeremiah 31:35-36). The LORD adds also that if the heavens can be measured and the center of the earth found, so will Israel be done (verse 37).
Ezekiel also makes it clear. “It is not for your sake, O house of Israel, that I am about to act, but for the sake of my holy name” (Ezekiel 36:22). “I will vindicate the holiness of my great name” (verse 23), “I will vindicate my holiness” (verse 24). “It is not for your sake that I will act, declares the Lord GOD; let that be known to you” (verse 32). “I am the LORD; I have spoken, and I will do it” (verse 36).
Has God changed His mind about these promises to act for His own name among the house of Israel? If it does not depend on them, if the whole point of this covenant is in fact that it depends solely on God, then when Israel rejected Jesus as their Messiah on the whole, how could that change the covenant? They hadn’t obeyed the 10 Commandments either. All the Israelites ever offered were hard-hearts, but, by God’s grace, soft hearts weren’t the condition of the covenant.
This is a one-sided promise made by God, kept by God, and for God. That makes it really good news.