Explanatory Notes on the Whole Bible, by John Wesley, [1754-65], at sacred-texts.com
isa 31:1Horses - For Egypt had many and choice horses.
isa 31:2He is safe - You think you are safe, in engaging the Egyptians; but God is not inferior to them in wisdom or strength, and therefore you have done foolishly, in preferring them before him, who will execute his judgments upon you, notwithstanding all the Egyptians can do. The help - The helpers, as it is explained in the next verse.
isa 31:3Flesh - Weak and frail.
isa 31:4For - Although you have done evil in sending to Egypt for help, yet the Lord himself will, of his own grace, give you that help which you do not deserve.
isa 31:5As birds - Which come from above, and so cannot be kept off; which fly swiftly, and engage resolutely, when their young ones are in danger. Passing over - The destroying angel shall pass over Jerusalem.
isa 31:8The sword - Not of any man, but of an angel. Discomfited - Heb. shall melt away, a great part of them being destroyed by the angel; and the hearts of the rest melting for fear.
isa 31:9He - Sennacherib shall flee away, from Jerusalem, to his strong city of Nineveh. The ensign - Of the Lord's ensign, which he hath lifted up against them. Whose fire - Who is, and will appear to be in Zion, like a fire to defend his people, and to consume their enemies.