| Gill's Exposition of the Entire Bible For the Lord your God is he that goeth with you,.... To battle, and therefore they had no reason to fear and be dismayed, to be fainthearted, terrified, and tremble: fear not, I am with thee,.... Isaiah 41:10, this, according to the Misnah (f), respects the ark, and so Jarchi, which was a symbol of the divine Presence, and went with them to battle; see Joshua 6:4. to fight for you against your enemies, to save you; to annoy and destroy the one, and to protect and save the other; thus far the anointed priest addressed the people in an oration to this purpose: the account Maimonides gives of it is, that"when they have set their ranks, and are near to a battle, the anointed of war stands on an high place, and all the ranks before him, and says to them in the holy tongue, "hear, O Israel", &c. unto to save you; and then another priest under him causes it to be heard by all the people with an high voice (g);''he repeated what the anointed of war had said, and expressed it with a loud voice, that all might hear. (f) Ut supra. (Misn. Sotab, c. 8. sect. 1.) (g) Hilchot Melachim, c. 7. sect. 3.
Geneva Study BibleFor the LORD your God is he that {b} goeth with you, to fight for you against your enemies, to save you. (b) Is present to defend you with his grace and power.
Jamieson-Fausset-Brown Bible Commentary4. your God is he that goeth with you, to fight for you against your enemies, to save you-According to Jewish writers, the ark was always taken into the field of combat. But there is no evidence of this in the sacred history; and it must have been a sufficient ground of encouragement to be assured that God was on their side.
Matthew Henry's Concise Commentary20:1-9 In the wars wherein Israel engaged according to the will of God, they might expect the Divine assistance. The Lord was to be their only confidence. In these respects they were types of the Christian's warfare. Those unwilling to fight, must be sent away. The unwillingness might arise from a man's outward condition. God would not be served by men forced against their will. Thy people shall be willing, Ps 110:3. In running the Christian race, and fighting the good fight of faith, we must lay aside all that would make us unwilling. If a man's unwillingness rose from weakness and fear, he had leave to return from the war. The reason here given is, lest his brethren's heart fail as well as his heart. We must take heed that we fear not with the fear of them that are afraid, Isa 8:12. | 
