He rested in the arm of flesh and soon dropped in death. David had faith in God. He used the means at hand-the stones and the sling. But it was his faith in the Almighty which delivered his people. Think of faith for a moment.
Faith cheerfully faces hardships.
It does not complain nor find Faith in God overcomes obstacles. David was just a youth, and the giant was a mature man of wide experience. Faith looks beyond all difficulties to God who is greater than all. Faith in God wins the victory every time. And this is the victory that overcometh the world, even our faith.