As birds flying, so will the LORD of hosts defend Jerusalem; defending also he will deliver it; and passing over he will preserve it.
As birds flying, so will the Lord of hosts defend Jerusalem. As in the image of "the lion" the point of comparison is the fearless might of Yahweh, so in that of the birds it is His solicitous affection (Deuteronomy 32:11; Psalms 91:4; Matthew 23:37).
Flying - or, which defend their young with their wings: to fly is a secondary meaning of the Hebrew х `uwp (H5774)] (Maurer). But the Septuagint, Chaldaic, Vulgate, Arabic, and Syriac support the English version. The allusion is to the same image employed in the Assyrian's threat against Jerusalem, Isaiah 10:14, "My hand hath found as a nest the riches of the people: and as one gathereth eggs that are left, have I gathered all the earth; and there was none that moved the wing" - namely, in defense. Here Yahweh engages to defend Jerusalem like the parent birds, hovering over their young to defend them from the hawk or vulture.
Passing over - as the destroying angel passed over (Hebrew, pasoach), so as to spare the blood-marked houses of the Israelites on the first Passover (Exodus 12:13; Exodus 12:23; Exodus 12:27). He passed, or leaped forward (Lowth), to destroy the enemy and to spare His people.