Charles Ellicott Commentary Isaiah 31:3

"Now the Egyptians are men, and not God; and their horses flesh, and not spirit: and when Jehovah shall stretch out his hand, both he that helpeth shall stumble, and he that is helped shall fall, and they all shall be consumed together." — Isaiah 31:3 (ASV)

The Egyptians are men ... —We hear again the keynote of Isaiah’s teaching. The true strength of a nation lay in its spiritual, not in its material, greatness: in seeking the Holy One of Israel by practising holiness. Without that condition the alliance with Egypt would be fatal both to those that sought for help and those who gave it.