Isaiah 54:10, spoken to forsaken-but-restored Zion in the wake of the Servant's atoning work (Isa 53), grounds Israel's security not in the mountains but in something more durable than they: "Though the mountains may be removed and the hills may be shaken, My loving devotion (חֶסֶד, chesed) will not depart from you, and My covenant of peace (בְּרִית שְׁלוֹמִי, berit shalom) will not be broken." The oracle is sealed like the Noahic oath (54:9) — an irrevocable, unilateral guarantee resting wholly on Yahweh's own faithfulness toward a people He once "forsook for a brief moment" (54:7). Jeremiah 31:31-34, the later text, announces the same theological substance in a different idiom: a divinely-guaranteed covenant for a restored people, set explicitly against the broken Sinai covenant (31:32), with Yahweh as sole agent (the seven first-person verbs of vv. 33-34) and an indestructibility that endures beyond exile. The connection is an Echo, not an allusion or quotation: the two prophets share no distinctive lexeme — Isaiah's covenant of peace and chesed are not Jeremiah's coinage berit chadashah ("new covenant"), and there is no verbal citation, only a converging conceptual profile of irrevocability, restoration, and unilateral divine guarantee (this is why the link belongs to Isaiah 54:10 and not, as the everlasting-covenant content might suggest, to the Isa 55:3 "sure mercies of David" oracle). The road to Christ runs through the Longitudinal Theme of Covenant, not typology — there is no type-and-antitype with escalation here, nor does either oracle fulfill the other; both are OT promises pointing forward, two strands of one canon-wide insistence that God will keep an unbreakable covenant with His people. Hebrews gathers both streams at the cross, fusing Isaiah's everlasting-covenant language with Jeremiah's new-covenant promise in "the blood of the eternal covenant" (Heb 13:20). And here the savoring lands: the believer's confidence is not the steadiness of the mountains but the steadiness of God's affection — His chesed that "will not depart" and His peace that "will not be broken," secured forever in Christ's blood, so that the soul rests not on its own covenant-keeping (which, like Sinai, breaks) but on a Husband-Redeemer whose loving devotion outlasts the hills. To behold Him is to want nothing more immovable.
