As birds flying, so will the Lord of hosts defend
Jerusalem
As the preceding metaphor expresses the mighty power of God, this his tenderness and affection, as well as his speed and swiftness in the deliverance of his people. As birds in the air, at a distance, especially the eagle, have their eye upon their nests, and their young ones in them, and when in danger fly to their assistance, and hover over them, and about them, to keep off those that would hurt them, or carry them away; so the Lord, on high, sees his people when in distress, and hastens to help them, and does surround, protect, and defend them: thus the Lord did, when Sennacherib with his army besieged Jerusalem; who boasted, with respect to other nations, that he had "found as a nest the riches of the people", and that "there was none that moved the wing against him", ( Isaiah 10:14 ) to which it is thought the allusion is here: defending also he will deliver [it];
from present distress, the siege of the Assyrian army: [and] passing over he will preserve [it];
passing over the city of Jerusalem to the army of the king of Assyria, that lay encamped against it; and smiting that by an angel with a sudden destruction, preserved the city from the ruin it was threatened with. The allusion is rightly thought to be to the Lord's passing over the houses of the Israelites, when he destroyed the firstborn in Egypt, ( Exodus 12:23 ) where the same word is used as here, and nowhere else.