1 Samuel 17:18

16And the Philistine drew near morning and evening, and presented himself forty days.

17And Jesse said unto David his son, Take now for thy brethren an ephah of this parched corn, and these ten loaves, and run to the camp to thy brethren;

18And carry these ten cheeses unto the captain of their thousand, and look how thy brethren fare, and take their pledge.

19Now Saul, and they, and all the men of Israel, were in the valley of Elah, fighting with the Philistines.

20And David rose up early in the morning, and left the sheep with a keeper, and took, and went, as Jesse had commanded him; and he came to the trench, as the host was going forth to the fight, and shouted for the battle.