1 Samuel 17:33, “Then Saul said to David, “You are not able to go against this Philistine to fight with him; for you are but a youth while he has been a warrior from his youth.” Exactly how old David was when he faced Goliath is unclear, but we know he was not a child as many would consider him to be. Saul would not have offered David his armor if it would not have fit him and Saul was a very large man as he stood head and shoulders above everyone. David although young was fully grown, he had killed a lion and a bear while protecting the sheep.