The phrase comes from Jeremiah 31:31 — the only place in the Old Testament where "new covenant" appears — and the first thing to notice is who it's promised to: "the house of Israel and the house of Judah." God announces it to a people in ruins, on the far side of a covenant they had broken: "not like the covenant that I made with their fathers... my covenant that they broke" (31:32). Mark where Jeremiah locates the fault: not in God's holiness, but in the covenant-breaking hearts of the people. The law could name what was good, but it could not remake its hearers from within. The new covenant therefore does more than relocate instruction: God forgives sin, writes his will within his people, and gives them his Spirit.
Three promises make it new. The law moves inside — "I will put my law within them, and I will write it on their hearts." Everyone within the covenant knows God personally — "they shall all know me, from the least of them to the greatest" (31:34), which in Jeremiah's sentence means everyone within the people, smallest to chief: knowledge of God no longer confined to an instructed class or inherited merely through membership in the nation. This does not eliminate mediation — Hebrews names Jesus himself the mediator of the new covenant (Hebrews 8:6) — it ends secondhand knowledge of God. And underneath both promises, the ground of it all: "I will forgive their iniquity, and I will remember their sin no more." Ezekiel heard the same promise as surgery: a heart of stone replaced with a heart of flesh, God's own Spirit put within (Ezekiel 36:26–27).
Jesus claims this promise at the table: "This cup that is poured out for you is the new covenant in my blood" (Luke 22:20) — he is announcing, on the night of his death, that Jeremiah's promise is now being enacted, and his blood is what seals it. Hebrews 8 quotes the Jeremiah passage in full and concludes that by calling this covenant "new," God has made the first one obsolete — old, aging, and ready to disappear. Hebrews does not treat the earlier covenant as God's failed experiment: it served its appointed purpose, but it could not perfect the worshiper, and its priesthood and repeated sacrifices now give way to Christ's once-for-all ministry.
And the nations? Their inclusion is real, but it stands on its own texts, not on Jeremiah 31:34: Gentiles who were once "strangers to the covenants of promise" are "brought near by the blood of Christ" (Ephesians 2:12–13) — grafted in, Paul says, like wild branches into a cultivated tree (Romans 11:17), sharing Israel's promise rather than replacing Israel's story. This is a summary you can hold against the texts — Jeremiah 31 and Hebrews 8 are the heart of the case; read them side by side and test it.
Jeremiah 31:31–34 — the promise itself; note who it addresses and what "least to greatest" means inside the sentence
Ezekiel 36:25–27 — the same promise as heart surgery
Luke 22:20 — Jesus seals it at the table
Hebrews 8:6–13 — Jeremiah quoted in full and the former covenant declared obsolete
2 Corinthians 3:3–6 — tablets of stone versus hearts; ministers of a new covenant
Ephesians 2:11–13 with Romans 11:17–24 — the nations' inclusion, on its own texts
Don't take this briefing's word for it — read these and test it.
Reformed covenant theology reads one covenant of grace across both testaments, with the new covenant as its fullest administration. Dispensational readers keep Jeremiah's promise addressed to Israel as a nation, with the church participating now and Israel's national fulfillment still ahead. Catholic and Orthodox teaching centers the new covenant in the Eucharist — the covenant meal Jesus instituted, renewed at every altar. Wesleyan and Baptist traditions emphasize the new birth and conscious faith as the covenant's entry. All agree on the center: the promise is God's doing, sealed in Christ's blood, resting on final forgiveness.
Two walls this topic must not rebuild. The new covenant does not mean God replaced Israel — the promise was made to Israel, and the nations join Israel's hope rather than confiscate it. Nor may distinctions between Israel and the church be used to rebuild the wall between Jewish and Gentile believers: Christ "has made us both one" (Ephesians 2:14). Any reading that erases Israel or reconstructs the wall of hostility has left these texts.
The new covenant is not merely an idea to master. Jesus announced it at a table, sealed it at the cross, and handed it to his gathered people in a cup — where it is still poured and the words are still spoken. Find that table.