What does Isaiah 7:13 mean?
The king of Judah has done a terrible thing. The Lord has promised Ahaz that the two kings who are now threatening him and Jerusalem will soon be out of the picture (Isaiah 7:8). He has also told Ahaz not to worry (Isaiah 7:4). Then God offered Ahaz the opportunity to see His power displayed. And to give him the assurance that God was with him and able to do as He promised (Isaiah 7:11). When people demand a miracle from God, that shows a lack of faith. Here, however, God is offering a sign and telling someone to choose the proof. So, declining the sign suggests he doesn't want confirmation of God's will.Ahaz could have asked for literally anything as a sign. He could have asked for his enemies to immediately turn and flee. Or even for the sun to turn black for a moment or even for great wisdom, as Solomon did. Instead, Ahaz turned God down (Isaiah 7:12). He asked for no sign from God and quoted Deuteronomy 6:16 out of context to pretend he was being pious. In truth, the king was disobeying God's command.
This is a significant turning point in God's relationship with both Ahaz and the nation of the Judah. Isaiah's response represents God's heart. He tells the house of David to listen. The house of David may mean Ahaz and his court in Jerusalem or it may mean the actual line of King David in its current form of Ahaz.
Isaiah states essentially, that Ahaz's decisions have been exhausting him and perhaps his people in Jerusalem. Now, Ahaz's choices are even making even God feel weary. The Lord knows that Ahaz is refusing miraculous confirmation, not because of faith, but because he wants to ignore God and do things his own way. In modern language, Ahaz might as well have told God "don't confuse me with facts, my mind is made up."
Isaiah's word choice shows just how things have changed between the Lord and Ahaz. In Isaiah 7:11, Isaiah tells Ahaz to ask for a sign from "your God." Now he says Ahaz has wearied "my God," no longer identifying a mutual Lord. The king has slipped into a dangerous position.