Standing in Faith
“If you are not firm in faith, you will not be firm at all.”
Isaiah isn’t just talking about any faith. He is specific. He’s talking about faith in God. Faith in anything else won’t work. Ahaz’s temptation was to put his faith in the king of Assyria. As strong as Assyria was, even they would not get him out of his predicament. As far as one could evaluate things based on what you could see, Assyria was his best option. They were a growing threat with a powerful army. They were, in fact, the reason Syria and Israel are teaming up and trying to get Ahaz to join them. But Isaiah is there to warn him against this temptation to walk only by sight. Instead, he must walk by faith in God.
To bolster that faith Isaiah gives him a sign; several actually. And it is these signs that give him reason to stand firm in his faith.