When thou goest out to battle against thine enemies, and seest horses, and chariots, and a people more than thou, be not afraid of them: for the LORD thy God is with thee, which brought thee up out of the land of Egypt. And it shall be, when ye are come nigh unto the battle, that the priest shall approach and speak unto the people, And shall say unto them, Hear, O Israel, ye approach this day unto battle against your enemies: let not your hearts faint, fear not, and do not tremble, neither be ye terrified because of them; For the LORD your God is he that goeth with you, to fight for you against your enemies, to save you. (Deuteronomy 20:1-4)
Speaking to the Israelites Moses passes on this commandment from God. When going into war that the Lord has led you to do not fear. When the enemy is bigger, fear not.
Throughout Scripture we are exhorted to trust God, to not worry, to not fear. If our hearts would tremble we must speak to them to have trust, we must abide in the beautiful rest that is found in following and submitting to His plan for our lives. God has promised to go before us, He has gone and has made away for us to go, all we must do is faithfully walk it out.
When we follow God and a trial arises we can take comfort in knowing God has led us here for our good and will lead us out. When the enemy rises up and appears to be bigger, stronger, faster, smarter, or even more rich, we must not fear. God has given us victory in the cross. But we must trust Him, so fear not. And if you do fear, cry out to Him. He will hear you, even in the midst of your trials.