1 Samuel 8:10-12

10And Samuel told all the words of Yhwh unto the people that asked of him a king. 11And he said, This will be the manner of the king that shall reign over you: He will take your sons, and appoint them for himself, for his chariots, and to be his horsemen; and some shall run before his chariots. 12And he will appoint him captains over thousands, and captains over fifties; and will set them to plow his ground, and to reap his harvest, and to make his instruments of war, and instruments of his chariots.