What does Isaiah 7:20 mean?
Isaiah continues to tell King Ahaz about the terrible days to come. This will happen because he refused to trust in the Lord to protect Judah (Isaiah 7:17). Instead, the king of Judah planned to ally with Assyria, hoping the king of Assyria would destroy Judah's enemies (2 Kings 16:7–9). To be allies, the much smaller nation of Judah would have to give something to Assyria in the form of payment or at least an agreement to be loyal to Assyria's king. In that sense, Ahaz literally "hired" Assyria to protect him.The idea of Ahaz trying to "hire" Assyria to protect Judah is mocked here by the Lord is saying He will hire the king of Assyria to "shave" Judah. The culture of Isaiah's time and place had much to do with honor and shame. For a man to be shaved against his will was a sign of great humiliation. Some commentators suggest that defeated enemies might have half their head shaved and that slaves were given specific shaved haircuts to show their status.
In this case, though, it is the Lord who will "shave" His people in Judah. The common belief of the times was that when one nation defeated another it was because the conquerors had stronger gods. Isaiah wants all who reads his words to understand that the gods of the Assyrians will not defeat the God of Israel. Instead, it will be the Lord who brings this humiliation on His own people for their faithlessness to Him. He will use the king of Assyria to shave the nation. Judah will be left exposed, ashamed, and beaten.