CHAPTER 31 Jun. 7 
No Safety in Egypt
Woe to those who go down to Egypt for help, and rely on horses and trust in chariots because they are many, and in horsemen because they are very strong, but they don’t look to the Holy One of Israel, and they don’t seek Yahweh! 2Yet He also is wise, and will bring disaster, and will not call back His words, but will arise against the house of the evildoers, and against the helpers of those who work iniquity. 3Now the Egyptians are men, and not God; and their horses flesh, and not spirit. When Yahweh stretches out His hand, both he who helps shall stumble, and he who is helped shall fall, and they all shall be consumed together. 4For thus says Yahweh to me, As the lion and the young lion growling over his prey who will not be dismayed if a multitude of shepherds is called together against him,  nor will he abase himself for their noise, so Yahweh of Armies will come down to fight on Mount Zion and on its mount. 5As birds hovering, so Yahweh of Armies will protect Jerusalem. He will protect and deliver it, He will pass over and preserve it. 6Return to Him from whom you have deeply revolted, children of Israel! 7For in that day everyone shall cast away his idols of silver and his idols of gold— the sin which your own hands have made for you. 8The Assyrian will fall by the sword, not of man; and the sword, not of mankind, shall devour him. He will flee from the sword, and his young men will become subject to forced labour. 9His rock will pass away by reason of terror, and his princes will be afraid of the banner, says Yahweh, whose fire is in Zion and His furnace in Jerusalem.

Commentary

31:3 The implication is that God also has horses and chariots- His invisible Angelic cherubim. Although Judah preferred to believe in the visible horses of Egypt, yet in His amazing grace, God still used His Angelic cherubim to destroy the Assyrians (37:36). This is grace itself.
31:4 Yahweh of Armies- God uses this title of Himself in this context to remind Judah that He has armies of Angels at His disposal. Judah were running to Egypt to enlist the help of their human armies; and by doing so were disbelieving that Yahweh really is the Yahweh of Armies of Angels. 
31:7 This means that at the time of the Assyrian siege of Jerusalem in Hezekiah’s time (which is the context of the chapter), the people were still worshipping idols. Yet Hezekiah had supposedly purged Judah of idols. This just shows that true faith is sometimes only found in a minority of God’s people; they may go along with the guidance of faithful leadership externally, but even good leaders cannot reform the hearts of individuals. It also shows how the Angelic deliverance of Jerusalem was due to the prayers and faith of a very small remnant, centred around Isaiah and Hezekiah.