Sources: Genesis 21–28; the covenant-transfer accounts.

Isaac is the son of promise — born to Sarah at advanced age (Gen 21), his birth establishing the supernatural character of the covenant line from the outset. His theological significance is mostly relational: he is the pivot through whom the covenant passes from Abraham to Jacob. Three episodes define him: (1) The binding (Akedah) (Gen 22) — God commands his sacrifice, then provides a ram substitute at the last moment. The ram is burned in his place. This is the foundational substitution narrative in the tradition — something dies so that the covenant line lives. The theological questions it generates (why would God command this? what does the substitute mean?) occupy interpreters for millennia after. (2) The marriage of Rebekah (Gen 24) — a divinely-guided search for a bride who will carry the covenant line; (3) The blessing stolen by Jacob (Gen 27) — Rebekah engineers Jacob’s receipt of the firstborn blessing, introducing the theme that covenant transmission operates through unexpected, even deceptive, means rather than simple birthright. The covenant line: Abraham → Isaac → Jacob. The parallel line — Ishmael — branches here and carries a different divine promise: great nation, twelve princes, blessing, but not the specific land-and-descendant covenant.