1 Samuel 17:15-20

15but David went back and forth from Saul to tend his father’s sheep at Bethlehem.

16For forty days the Philistine came forward every morning and evening and took his stand. 17Now Jesse said to his son David, “Take this ephah That is, probably about 36 pounds or about 16 kilograms of roasted grain and these ten loaves of bread for your brothers and hurry to their camp. 18Take along these ten cheeses to the commander of their unit. See how your brothers are and bring back some assurance Or some token; or some pledge of spoils from them.

19They are with Saul and all the men of Israel in the Valley of Elah, fighting against the Philistines.” 20Early in the morning David left the flock in the care of a shepherd, loaded up and set out, as Jesse had directed. He reached the camp as the army was going out to its battle positions, shouting the war cry.