The Lord of hosts is with us - See Psalm 46:7. This is the conclusion, or the result of the whole. As applied to the invasion of Sennacherib, this would be clearly seen, for all that occurred in that invasion was adapted to leave the impression that Jehovah, God of hosts, was with the Hebrew people. He had interposed in time of danger; he had saved his city and nation; he had overthrown one of the most mighty armies that had ever been assembled; he had caused the boasting conqueror himself to retrace his steps to his capita; he had wholly delivered the nation from all danger; and he had shown how easy it was, in ways which they could not have anticipated, to bring deliverance. The truth thus conveyed was adapted to the people of God in all lands and at all times, as showing that God has power to defend his people against the most formidable enemies, and that all their interests are safe in his hands.

The Lord of hosts is with us - Having heard these declarations of God, the people cry out with joy and exultation, The Lord of hosts, the God of armies, is with us; we will not fear what man can do unto us.
The God of Jacob is our refuge - He who saved our fathers will save us, and will never abandon his people in distress.
Selah - This is a firm, lasting, unshaken, well-tried truth.

The Lord of hosts is with us; the God of Jacob is our refuge. See Gill on Psalm 46:7. The Targum paraphrases it, "the Word of the Lord of hosts", as in Psalm 46:7; and the same words are here repeated, to comfort those that were fearful and unbelieving, with which the church then comforted herself.
Selah; on this word; see Gill on Psalm 3:2.

Be still - Stir no more against my people. God - The only true and almighty God; your gods are but dumb and impotent idols. Exalted - I will make myself glorious by my great and wonderful works.