The Lord of hosts [is] with us; the God of Jacob [is] our refuge. See Gill on "Ps 46:7". The Targum paraphrases it, "the Word of the Lord of hosts", as in Ps 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 "Ps 3:2".