Charles Ellicott Commentary 1 Samuel 17:37

"And David said, Jehovah that delivered me out of the paw of the lion, and out of the paw of the bear, he will deliver me out of the hand of this Philistine. And Saul said unto David, Go, and Jehovah shall be with thee." — 1 Samuel 17:37 (ASV)

Go, and the Lord be with you. —This permission and blessing of King Saul recalls the Saul of former days, before the covenant between him and the Mighty One of Israel was broken, before the Spirit of the Lord had departed from him. It was a great act of courageous trust in the Glorious Arm which, Saul knew, had so often fought for Israel.

We must bear in mind that this was no mere duel between two fighting men, an Israelite and a Philistine. Rather, the fortunes of the nation for an indefinite period were to be staked on this momentous single combat between a tried warrior of gigantic strength and a boy quite unaccustomed to military exercises. As we will soon see, this boy was also a stranger even to a soldier’s uniform and military equipment.