Exodus 14:14. the Lord will fight for you; you need only be still.
Why is it so hard for us and our human nature to trust God? The Israelites have witnessed the greatest display of God's power since creation, and still they do not trust. God has brought them safely out of bondage and is leading them visibly through the desert with a pillar of cloud by day and of fire by night. He is in near constant communication with Moses.
God has led more than a million Israelites (his entire favored nation) to a campsite next to the Red Sea. The people turn and they see more than 600 chariots and all the Egyptian officers/soldiers bearing down on them quickly. Immediately their thoughts turn back to the recent days of captivity and slave labor...surely those days weren't as bad as they remembered. Anything would be better than the thought of impending slaughter.
I imagine the men were arming up to try to protect their families as best they could when Moses told them to be still and watch the Lord fight for them. Have you ever been in a situation where you wanted to fight back, but were unable to do anything? I think of situations where a loved one is gravely ill -- there is nothing that you can do but sit and watch. You feel so helpless.
Yet God is carrying on the fight for us. He may be using doctors and experts, or He may be in the process of bringing a loved one home to ease their suffering. Hard as it is, we just have to trust Him to know what is best and to fight the battle for us.
God, help us to be still and know that you are in control!