But how could this sequence of events, which required time for its unfolding, be 'a sign'? We must somewhat modify our notions of a sign to understand the prophet. The Scripture usage does not only designate by that name a present event or thing which guarantees the truth of a prophecy, but it sometimes means an event, or sequence of events, in the future, which, when they have come to pass in accordance with the divine prediction of them, will shed back light on other divine words or acts, and demonstrate that they were of God. Thus Moses was given as a sign of his mission the worshipping in Mount Sinai, which was to take place only after the Exodus. So with Isaiah's sign here. When the harvest of the third year was gathered in, then Israel would know that the prophet had spoken from God when he had sung Sennacherib's defeat. For the present, Hezekiah and Judah had to live by faith; but when the deliverance was complete, and they were enjoying the fruits of their labours and of God's salvation, then they could look back on the weary years, and recognise more clearly than while these were slowly passing how God had been in all the trouble, and had been carrying on His purposes of mercy through it all. And there will be a 'sign' for us in like manner when we look back from eternity on the transitory conflicts of earthly life, and are satisfied with the harvest which He has caused to spring from our poor sowings to the Spirit. The definite promise of deliverance in verses 32-34 is addressed to Judah, and emphasises the completeness of the frustration of the invader's efforts. There is a climax in the enumeration of the things that he will not be allowed to do--he will not make his entry into the city, nor even shoot an arrow there, nor even make preparation for a siege. His whole design will be overturned, and as had already been said (ver. 28), he will retrace his steps a baffled man. Note the strong antithesis: 'He shall not come into this city, ... for I will defend this city.' Zion is impregnable because Jehovah defends it. Sennacherib can do nothing, for he is fighting against God. And if we 'are come unto the city of the living God,' we can take the same promise for the strength of our lives. God saves Zion 'for His own sake,' for His name is concerned in its security, both because He has taken it for His own and because He has pledged His word to guard it. It would be a blot on His faithfulness, a slur on His power, if it should be conquered while it remains true to Him, its King. His honour is involved in protecting us if we enter into the strong city of which the builder and maker is God. And 'for David's sake,' too, He defends Zion, because He had sworn to David to dwell there. But Zion's security becomes an illusion if Zion breaks away from God. If it becomes as Sodom, it shares Sodom's fate.