Andrew Abernethy on the "sign" in Isaiah 7:14

First, it is impossible to reconcile the date of this child's birth (c. 733 BC) with that of Hezekiah, who becomes king after Ahaz. Second, the house of David is not the exclusive object of foreign threat and God's punishment. While King Rezin and Pekah seek to displace King Ahaz (7:6), they are also attacking Jerusalem (7:1) and desire to conquer and divide up Judah (7:6). What is more, while King Ahaz is said to be fearful (7:2) and it rebuked for faithlessly rejecting God's offer of a sign (7:12-13), 'his people' also fear (7:2), and a plurality of people are exhorted to believe in God (7:9). God's judgment, then, is not simply against Ahaz and the house of David (7:13, 17), but days of calamity will also come upon 'your people', probably the nation as a whole (7:17). The sign, then, does not necessarily have to be limited to God's plans with the house of David, but instead could be focusing upon the circumstances facing the entire nation. (Andrew T. Abernethy, The Book of Isaiah and God's Kingdom: A thematic-theological approach [vol. 40 New Studies in Biblical Theology; Downers Grove, Illin.: Intervarsity Press, 2016], 122-23)