Deuteronomy 20:1

“And he shall say to them, ‘Hear, O Israel, you are drawing near to the battle against your enemies today. Do not let your heart be faint. Do not be afraid, nor be alarmed, nor be in dread before them,

“Be strong and courageous. Do not be afraid or be in dread of them, for Yahweh your God is the one who goes with you. He will not fail you or forsake you.”

And David said to Saul, “Let no man’s heart fail on account of him; your servant will go and fight with this Philistine.”

and he said, “Pay attention, all Judah and the inhabitants of Jerusalem and King Jehoshaphat: thus says Yahweh to you, ‘Do not fear or be dismayed because of this great multitude, for the battle is not yours but God’s.

‘Do not fear, for I am with you; Do not anxiously look about you, for I am your God. I will make you mighty, surely I will help you; Surely I will uphold you with My righteous right hand.’

Statutes About Warfare