Isaiah 7:13

Isaiah saw right through the king’s hypocrisy. He warned him by addressing him as the representative of the house of David. The plural "you" indicates that Isaiah was addressing all the members of the house of David and perhaps the whole nation (cf. Isaiah 7:9). Yahweh had made covenant promises that David’s dynasty would continue forever (2 Samuel 7:16; 1 Kings 8:25). Ahaz should not have feared being replaced by a puppet king (Isaiah 7:6). Ahaz had said he would not test God (Isaiah 7:12), but by refusing to ask for a sign, that is precisely what he was doing-testing God’s patience with him. He was also testing the patience of the godly in Israel who were looking to their king to trust God. The prophet had called Yahweh "Ahaz’s God" (Isaiah 7:11), but now that the king had rebelled against Him, Isaiah referred to the Lord as "my (Isaiah’s) God." This change was ominous, suggesting that God would abandon the king. If Ahaz’s decision resulted in God withdrawing support from the Davidic kings, the prophecy of Immanuel may imply that God would raise up His own King from David’s house who would be faithful to Him. This could explain why God gave such a major messianic prediction at this time.

"To appreciate fully the messianic portrait of Isaiah 1-39, it must be viewed against the backdrop of the generally negative presentation of Judahite kingship in these same chapters." [Note: Chisholm, A Theology . . ., p. 314.]