Chapter 22 The Burden of the Valley of Vision.
The vision begins with a description of wild rejoicing in Jerusalem at something which is the cause of great happiness. Some see this rejoicing as resulting from their receiving the news that their initial plea to Assyria for merciful treatment had been accepted (prior to the later advancement on Jerusalem. See 2 Kings 18:13-16). But if that were so why is this earlier incident not mentioned in Chapter s 36-39? Others see it as resulting from the retreat of Assyria from the siege of Jerusalem after the slaying of a large part of their army by Yahweh during the siege (36-37). But would not Isaiah have also rejoiced in Yahweh's deliverance and drawn pointed lessons? And why the still strong sense of the approach of death (Isaiah 22:13)? Still others refer it to their rejoicing on the inauguration of the Siloam Tunnel for bringing water into Jerusalem, or on the day when the tunnellers first met and the water broke through, instilling a new joyous confidence into Jerusalem, but foreboding in Isaiah because of their false confidence (Isaiah 22:8-11). A further suggestion is that it was on their receiving the news that a large Egyptian army was on the way to hopefully effect their deliverance. The truth is that it could really be any time when good news was brought to Jerusalem, after prior ignominious failure.
But whatever its cause Isaiah disapproves of it. He feels that they have nothing to rejoice over and everything to be ashamed of. He is fearful for the future because of their self-confidence. He knows that this is not trust in Yahweh, it is trust in themselves. What they should be doing is worshipping Yahweh and giving thanks to Him in all humility and shame, recognising that had they but trusted in Yahweh from the beginning none of the things that had come on them would have happened, and that trust in Yahweh now could bring them deliverance. But instead, even now, they rather look to other gods in their housetop shrines.