Bible Notes Online - Isaiah 20 - ESV
Commentary

v1: The time of Assyria's attack upon Philistia, Ashdod being a Philistine town, and allied to Egypt.

v2: Isaiah himself, a sign to the people, as in 8.18. The prophet had to live his message. He became like a prisoner; compare Ezek 24.16-24 and Hos 1-3.

v3-4: The lesson, that Assyria would defeat Egypt and Cush; a short term prophecy, contrasting with the longer term prediction of 19.24-25.

v5-6: It is folly to put our hope in man; a warning to the people of God then, and today.