11 He said, “This is what the king who will reign over you will claim as his rights: He will take your sons and make them serve with his chariots and horses, and they will run in front of his chariots.
12 Some he will assign to be commanders of thousands and commanders of fifties, and others to plow his ground and reap his harvest, and still others to make weapons of war and equipment for his chariots.

References for 1 Samuel 8:12