A commentary on Exodus 14:13-31 says this:
Moses was a man of faith who knew that Pharaoh's army was no threat to Jehovah. He gave several commands to the people, and the first was, "Fear not" (v. 13). Sometimes fear energizes us and we quickly try to avoid danger, but sometimes fear paralyzes us and we don't know what to do. Israel was tempted to flee, so Moses gave his second command: "Stand still, and see the salvation of the Lord" (v. 13). By faith the Jews had marched out of Egypt, and now by faith they would stand still and watch God destroy the Egyptian charioteers.
Moses not only told them to stand still, but also to "be still" (v. 14). How easy it would have been to weep, complain, and keep criticizing Moses, but none of those things would have helped them out of their predicament. Unbelief complains, but faith obeys and brings glory to the Lord. "Be still, and know that I am God" (Ps 46:10). What is there to complain about when we have the wonderful promise, "The Lord shall fight for you"? (Ex 14:14) Later in their journey, the Lord would help Joshua and the Jewish army fight their battles (17:8); but this time, God would defeat the Egyptians without Israel's assistance.
(from The Bible Exposition Commentary: Old Testament © 2001-2004 by Warren W. Wiersbe. All rights reserved.)
Do we have the faith today to stop and let God fight for us? Do we trust Him with our all and allow His mighty hand to destroy sickness? Deal with a situation? Restore relationships? Bring justice? Don't be hasty in taking things on your own shoulders. Jesus hung on the cross for our freedom and triumph over the enemy. He take our burdens and gives us his. Let God be God and be still. He will fight for you.
Moses answered the people, "Do not be afraid. Stand firm and you will see the deliverance the Lord will bring you today. The Egyptians you see today you will never see again. 14 The Lord will fight for you; you need only to be still."