David's armor

 Then Saul clothed David with his armor. He put a helmet of bronze on his head and clothed him with a coat of mail, and David strapped his sword over his armor. And he tried in vain to go, for he had not tested them. Then David said to Saul, “I cannot go with these, for I have not tested them.” So David put them off. Then he took his staff in his hand and chose five smooth stones from the brook and put them in his shepherd’s pouch. His sling was in his hand, and he approached the Philistine.

1 Samuel 17:38‭-‬40 ESV

David realized as soon as he tried on the armor that he was trying to be something he wasn't. When doing God's work you have to stay true to yourself. David could have proved to be a mighty warrior in wearing the king's armor, instead he picked 5 smooth stones and a slingshot, because that is what he was talented at.