Isaiah 20

3. three years--Isaiah's symbolical action did not continue' all this time, but at intervals, to keep it before the people's mind during that period [ROSENMULLER]. Rather, join "three years" with "sign," a three years' sign, that is, a sign that a three years' calamity would come on Egypt and Ethiopia [BARNES], ( Isaiah 8:18 ). This is the only instance of a strictly symbolical act performed by Isaiah. With later prophets, as Jeremiah and Ezekiel, such acts were common. In some cases they were performed, not literally, but only in prophetic vision.
wonder--rather, "omen"; conveying a threat as to the future [G. V. SMITH].
upon--in reference to, against.

4. buttocks uncovered--Belzoni says that captives are found represented thus on Egyptian monuments ( Isaiah 47:2 Isaiah 47:3 , Nahum 3:5 Nahum 3:8 Nahum 3:9 ), where as here, Egypt and Ethiopia are mentioned as in alliance.

5. they--the Philistine allies of Egypt who trusted in it for help against Assyria. A warning to the party among the Jews, who, though Judah was then the subordinate ally of Assyria, were looking to Egypt as a preferable ally ( Isaiah 30:7 ). Ethiopia was their "expectation"; for Palestine had not yet obtained, but hoped for alliance with it. Egypt was their "glory," that is, boast ( Isaiah 13:19 ); for the alliance with it was completed.

6. isle--that is, coast on the Mediterranean--Philistia, perhaps Phoenicia (compare Isaiah 23:2 , 11:11 , 13:22 , Psalms 72:10 ).
we--emphatical; if Egypt, in which we trusted, was overcome, how shall we, a small weak state, escape?