1 Samuel 17:12-17

12Now 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.

13The 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.

14David was the youngest. The three eldest followed Saul,

15but David went back and forth from Saul to feed his father's sheep at Bethlehem.

16For forty days the Philistine came forward and took his stand, morning and evening.

17And Jesse said to David his son, "Take for your brothers an ephah of this parched grain, and these ten loaves, and carry them quickly to the camp to your brothers.