Isaiah 20:5,6

‘And they will be dismayed and ashamed, because of Cush their expectation, and of Egypt their glory. And the inhabitant of this coastland will say in that day, “Behold, such is our expectation, where we fled for help to be delivered from the king of Assyria, and we, how will we escape?” '

Thus would Philistia (‘this coastland'), and all who trusted in Egypt recognise their folly in placing confidence in Cush and Egypt. Cush had been their grounds of confidence, Egypt their strongest resource, in whom they had boasted, and they were to be first soundly defeated, and then invaded and crushed. Thus the Philistines and their allies would recognise that in view of this all hope had gone. They had no way of escape. So let Hezekiah beware of trusting in Egypt.

The warning comes to us to that we should not put our final trust in anything or anyone but God, Who alone will not let us down.