1 Samuel 17:20
"And 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."
Cross References (ranked by relevance)
And David arose, and came to the place where Saul had pitched: and David beheld the place where Saul lay, and Abner the son of Ner, the captain of his host: and Saul lay in the trench, and the people pitched round about him.
For the days shall come upon thee, that thine enemies shall cast a trench about thee, and compass thee round, and keep thee in on every side,
So David and Abishai came to the people by night: and, behold, Saul lay sleeping within the trench, and his spear stuck in the ground at his bolster: but Abner and the people lay round about him.
And Eliab his eldest brother heard when he spake unto the men; and Eliab’s anger was kindled against David, and he said, Why camest thou down hither? and with whom hast thou left those few sheep in the wilderness? I know thy pride, and the naughtiness of thine heart; for thou art come down that thou mightest see the battle.