Context: Isaiah is the greatest of the prophets and the most quoted book in the New Testament — over 400 citations or allusions. Called the "Gospel of the OT" or the "fifth Gospel," Isaiah prophesied in Jerusalem during the reigns of four kings: Uzziah, Jotham, Ahaz, and Hezekiah (740–700 BC), a ministry of about 40 years.

Structure: The book divides into two major sections: Isaiah 1–39 ("proto-Isaiah"), focused on the judgment of Israel, Judah, and the nations, culminating in the historical episode of the Assyrian invasion and Jerusalem's miraculous deliverance under Hezekiah; and Isaiah 40–66 ("deutero/trito-Isaiah"), focused on consolation, restoration, and eschatological salvation, addressed to the Babylonian exile community and beyond.

Messianic prophecy: The four "Servant Songs" (42; 49; 50; 52–53) are the apex of pre-Christian messianism. Isaiah 53 — the servant pierced "for our transgressions, crushed for our iniquities; upon him was the chastisement that brought us peace" — is the most explicit messianic text of the OT and was widely cited by the apostles. Isaiah also prophesied the virgin birth (7:14), the Prince of Peace (9:6–7), and the new creation (65–66).