1 Samuel 17:17

David was the youngest; and the three oldest followed Saul.

Now David went back and forth from Saul to feed his father’s sheep at Bethlehem.

The Philistine came near morning and evening, and presented himself forty days.

and bring these ten cheeses to the captain of their thousand; and see how your brothers are doing, and bring back news.”

Now Saul, and they, and all the men of Israel were in the valley of Elah, fighting with the Philistines.

David rose up early in the morning and left the sheep with a keeper, and took the provisions and went, as Jesse had commanded him. He came to the place of the wagons as the army which was going out to the fight shouted for the battle.