What did King David say to convince King Saul to let him battle Goliath?

315 In this episode, I continue to teach how you and I need to
walk in more spiritual power.

I use the story of David and Goliath to illustrate my point.
Still, since I've already taught about the power of your words
and how King David defeated Goliath before he threw the smooth
stone, I use several Bible verses to make my point. 

1 Samuel 17:31-37 and 1 Samuel 17:55-58