1 Samuel 17:14-19

David was the youngest. The three eldest followed Saul, but David went back and forth from Saul to feed his father’s sheep at Bethlehem. For forty days the Philistine came forward and took his stand, morning and evening. And Jesse said to David his son, “Take for your brothers an ephah of this parched grain, and these ten loaves, and carry them quickly to the camp to your brothers. Also take these ten cheeses to the commander of their thousand. See if your brothers are well, and bring some token from them.” Now Saul and they and all the men of Israel were in the Valley of Elah, fighting with the Philistines.