When I am afraid,
I put my trust in you.
In God, whose word I praise,
in God I trust; I shall not be afraid.
What can flesh do to me?
In the confidence of past deliverance David bravely sang out this prayer. He boldly trusted God in the midst of attack from people bent on his destruction. God was His strength even as enemies did their worst to attempt to wipe him out. David's fear was real. But so was his faith.
David does not dodge fear, he acknowledges it. He reports that there are situations where he is really afraid for his life. There is a real threat that this prayer is reporting. He is afraid. But even in that real threat, the choice was made to live beyond that fear and to "put trust" consciously in God. This is a deliberate action to not let the feeling of fear overcome David's faith. Instead, there is this very deliberate faith. Faith is David's chosen commitment to fight off fear and let God fight off those who are seeking his life.
David's faith is deliberate and there are two actions that accompany his choice of faith that help us understand how he could overcome the overwhelming feeling of fear. First, David worshiped God at His Word. He trusted God because of the Word of God. From scripture David learned about the faithfulness and protection God gave His people. From God's Word David drew faith to believe. He praised God for His Word and it gave him the capacity to trust beyond fear.
The second action is found in a rhetorical question: "What can flesh do to me?" David compares the all-powerful God to the limited strength of human foes. And there is no comparison. Man can only do what the Lord wills. And it is this limitation that strengthens faith. Man can only act, even sinfully, within the realm of God's sovereignty. Man cannot take David's soul, for it belongs to God. David's faith could confidently trust God Who rules all things, even the outcomes of human interaction. And so real fear's terror ended in real faith's trust.