In all fairness, David tried it. He put on Saul's armor but he found it too heavy and cumbersome... to restrictive. David was not used to this. How could he fight wearing these things? He certainly had not needed them when he killed the lion and the bear. The only armor, the only weapon he needed was God.
He rejected the armor and the weapons of the king.
To the onlookers, this was not only suicidal, it was crazy. David would be killed! David however, refused to put his trust in the weapons of man and refused to put himself under the protection of the king. Even Goliath thought David was crazy and was making a mockery of him. David's response was:
And everyone assembled here will know that the Lord rescues his people, but not with sword and spear. This is the Lord’s battle, and he will give you to us!- 1 Samuel 17:47 (NLT)
We put our confidence in a lot of things. We put our confidence in legalism, good works, our own intelligence, our position, wealth, spouse, family, friends and even people in the Church. This list is not exhaustive!
Our hope, our confidence must be in God and in God alone. If it is not, we do not stand a chance against the enemy. Is your hope and confidence in God and God alone?