When the words were heard which David spoke, they rehearsed them before Saul; and he sent for him.
Notice that in Saul's reluctance to approve David as his champion, he did not mention David's physical stature, his strength or his height, but only his age.  The notion that David was a "mere lad" or an "immature stripling" at this time is contradicted by the fact of his being able to put on the king's armor.  Saul was head and shoulders above all the people; and this passage states that David also was a man of immense physical power and every whit as tall as the king himself.  It is amazing to this writer how few commentators even notice this fact.  "The fact that David tried on the armor of Saul indicates that he approximated the height of Saul."[17]