Charles Ellicott Commentary Deuteronomy 33:27

"The eternal God is [thy] dwelling-place, And underneath are the everlasting arms. And he thrust out the enemy from before thee, And said, Destroy." — Deuteronomy 33:27 (ASV)

The eternal God is your refuge.—The word “your” is not represented in the original. Mâ’ônah, the word for refuge, differs very slightly from the “refuge” of Psalms 90:1, Lord, you have been our refuge in generation and generation, which are also the words of Moses. The same word is used of the “habitation of Jehovah” in heaven (Deuteronomy 26:15). Perhaps we should connect this clause with what precedes, and render the passage thus:—

“There is none like the God of Jeshurun,
Riding on the heavens for your help,
And in His Majesty on the sky—
The dwelling of the eternal Jehovah (above you)
And underneath, the everlasting arms!
And He will expel before you (every) enemy,
And will say (to you), Destroy them.”