““In context, the son of Isa 7:14 was a sign to King Ahaz, and was probably Isaiah’s own son (Isa 7:10–17; 8:3–4). Isaiah’s children’s names were for “signs” to Israel (Isa 8:18). Nevertheless, Isaiah’s son signified not only immediate deliverance in their own time, but pointed to the ultimate deliverance with the future birth of the ultimate Davidic ruler (Isa 9:6–7; cf. Isa 11:1–5). That would be the ultimate fulfillment of the promise of “Immanuel” (Isa 7:14), “God with us”: the king would himself be the “Mighty God” (Isa 9:6), a title for God elsewhere in Isaiah (Isa 10:21). Matthew has in mind the context of the entire section of Isaiah, which he again cites soon afterward (see Isa 9:1–2 in Mt 4:15–16).””
