John Calvin Commentary Isaiah 31:5

"As birds hovering, so will Jehovah of hosts protect Jerusalem; he will protect and deliver [it], he will pass over and preserve [it]." — Isaiah 31:5 (ASV)

As birds that fly. This is the second comparison, by which the Prophet shows how great care the Lord takes of us, and how earnestly He is determined to make us happy. It is taken from birds, which are prompted by astonishing eagerness to preserve their young; for they almost kill themselves with hunger and shrink from no danger, so that they may defend and preserve their young. Moses makes use of the same comparison when, reproaching the people for their ingratitude, He compares the Lord to an eagle

laying her nest, spreading her wings, and fluttering over her young (Deuteronomy 32:11).

Christ also remonstrates with Jerusalem:

How often would I have gathered your children together, as a hen gathers her chickens, and you would not! (Matthew 23:37).

The sum of this passage is that the Lord will be sufficiently powerful to defend His people, for whom He has a special love and a peculiar care. What Moses relates that God did, Isaiah promises that He will always do; for He will never forsake those whom He has once received into His favor.

So that no one, therefore, should imagine that this statement related only to the people of a single age, He expressly declares that God will spread His wings to defend Jerusalem. Nor is it without reason that He mentions not only Mount Zion but its hill; for on that hill was built the temple in which God desired that people should call upon Him.

Wherever, therefore, the worship of God is pure, let us know that salvation will be certain; for people cannot call upon Him in vain.

Let us be His people, and, on the other hand, He will be our God. (Leviticus 26:12).