1 Samuel 17:12-15

Now David was the son of the Ephrathite of Bethlehem in Judah, whose name was Jesse, and he had eight sons. And Jesse was old in the days of Saul, advanced in years among men. The three older sons of Jesse had gone after Saul to the battle. And the names of his three sons who went to the battle were Eliab the firstborn, and the second to him Abinadab, and the third Shammah. David was the youngest. Now the three oldest followed Saul, but David went back and forth from Saul to tend his father’s flock at Bethlehem.