What makes you quiver? It’s a fundamental question.
Isaiah sees Yahweh enthroned, and hears the voice of thunder that makes the posts of the house to quiver (6:4). Elsewhere, Yahweh makes the idols of Egypt shake in fear (19:1), and the earth itself (24:20). The wine of His judgment makes nations quiver and stagger and fall (29:9).
That doesn’t move Ahaz. But when Ahaz hears about a confederation of Aram and Israel, his heard shakes within Him, and so too the hearts of all Judah (7:2).
Isaiah underscores the contrast with a series of puns. “Make alliance” or “camp” in 7:2 is nuach , to rest or come to rest, the verb from which Noah’s name is drawn. When the Arameans nuach in Etphraim, the heart of Ahaz begins to quiver, nua’ (whose ancient pronunciation might have been much closer to nuach , if the ayin was vocalized). The verse closes with an additional pun: Hearts quiver ( nua’ ) like trees quiver ( nua’ ) before the face of the wind ( ruach , also “spirit”).
Ahaz quivers at the anger of Rezin and Pekah (7:4), but their smoke and fire is nothing compared to the fire of Yahweh (6:1-4). Quiver at the anger of Yahweh, Isaiah tells the king (cf. 5:25).