Commentators note Isaiah's shift from addressing Ahaz with "the Lord your God" to rebuking the "house of David" and speaking of "my God." This change signifies a separation. By rejecting God's offered sign, the king and his court have forfeited their claim on God, who is now claimed by the faithful prophet. The address "house of David" is used not as an honor, but as a reproach to highlight how far they had fallen from their faithful ancestor.