1 Samuel 17:12-15

Now David was the son of an Ephrathite of Bethlehem in Judah, named Jesse, who had eight sons. In the days of Saul the man was already old and advanced in years. The three oldest sons of Jesse had followed Saul to the battle. And the names of his three sons who went to the battle were Eliab the firstborn, and next to him Abinadab, and the third Shammah. 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.