1 Samuel 17:18

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.

Jesse said to David his son, “Now take for your brothers an ephah of this parched grain and these ten loaves, and carry them quickly to the camp to your brothers;

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.

Israel and the Philistines put the battle in array, army against army.