What does Isaiah 19:16 mean?
The narrative of this chapter suddenly transitions from a prophecy against Egypt (Isaiah 19:1) to a prediction of the far future. Isaiah switches to talking about the latter days—sometimes called the "end times"—when the Lord will defeat Israel's enemies and the unite the world by ruling over all from His throne in Jerusalem (Isaiah 2:1–5; Revelation 20:1–4).When that future day comes, the Egyptians will be terrified by the obvious power of God. This will not be inspired by Judah as some military superpower. It will be due to the power of the Lord made obvious on earth. As Egypt trembled before the Lord during the time of Moses (Exodus 10:7; 12:33), she will once again recognize the power of Israel's God to destroy her. That Egypt becomes "like women" uses a warlike context. In that culture, women were not combatants; the implication is that the entire nation will be utterly helpless against what has happened.
Once again, Isaiah wants the people of Judah to understand that they do not need Egypt to keep them safe from those who threaten them. When the day of the Lord comes, it will be Egypt who cowers in fear before the Lord and His people.