Jesaja 20:5

But if Egypt and Ethiopia are thus shamefully humbled, what kind of impression will this make upon those who rely upon the great power that is supposed to be both unapproachable and invincible? "And they cry together, and behold themselves deceived by Ethiopia, to which they looked, and by Egypt, in which they gloried. And the inhabitant of this coast-land saith in that day, Behold, thus it happens to those to whom we looked, whither we fled for help to deliver us from the king of Asshur: and how should we, we escape?" אי, which signifies both an island and a coast-land, is used as the name of Philistia and Zep 2:5, and as the name of Phoenicia in Isa 23:2, Isa 23:6; and for this reason Knobel and others understand it here as denoting the former with the inclusion of the latter. But as the Assyrians had already attacked both Phoenicians and Philistines at the time when they marched against Egypt, there can be no doubt that Isaiah had chiefly the Judaeans in his mind. This was the interpretation given by Jerome ("Judah trusted in the Egyptians, and Egypt will be destroyed"), and it has been adopted by Ewald, Drechsler, Luzzatto, and Meier. The expressions are the same as those in which a little further on we find Isaiah reproving the Egyptian tendencies of Judah's policy. At the same time, by "the inhabitant of this coast-land" we are not to understand Judah exclusively, but the inhabitants of Palestine generally, with whom Judah was mixed up to its shame, because it had denied its character as the nation of Jehovah in a manner so thoroughly opposed to its theocratic standing. Unfortunately, we know very little concerning the Assyrian campaigns in Egypt. But we may infer from Nah 3:8-10, according to which the Egyptian Thebes had fallen (for it is held up before Nineveh…

This chapter is a prediction of the carrying away of multitudes both of the Egyptians and the Ethiopians into captivity by the king of Assyria. Here is, I. the sign by which this was foretold, which was the prophet's going for some time barefoot and almost naked, like a poor captive (Isa 20:1-2). II. The explication of that sign, with application to Egypt and Ethiopia (Isa 20:3-5). III. The good use which the people of God should make of this, which is never to trust in an arm of flesh, because thus it will deceive them (Isa 20:6).

20:5-6 Philistia’s downfall was a warning to the people of Judah, who also relied on Egypt and other alliances rather than on God.