1 Samuel 17:39

David strapped his sword over the tunic and tried to walk, but he was not accustomed to them. “I cannot walk in these,” David said to Saul. “I am not accustomed to them.” So David took them off.

And David girded his sword upon his armour, and he assayed to go; for he had not proved it. And David said unto Saul, I cannot go with these; for I have not proved them. And David put them off him.