Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[193] NOW the women were an occasion of Saul's envy and hatred to David; for they came to meet their victorious army with cymbals, and drums, and all demonstrations of joy, and sang thus: The wives said, that "Saul had slain his many thousands of the Philistines." The virgins replied, that "David had slain his ten thousands." Now, when the king heard them singing thus, and that he had himself the smallest share in their commendations, and the greater number, the ten thousands, were ascribed to the young man; and when he considered with himself that there was nothing more wanting to David, after such a mighty applause, but the kingdom; he began to be afraid and suspicious of David. Accordingly he removed him from the station he was in before, for he was his armor-bearer, which, out of fear, seemed to him much too near a station for him; and so he made him captain over a thousand, and bestowed on him a post better indeed in itself, but, as he thought, more for his own security; for he had a mind to send him against the enemy, and into battles, as hoping he would be slain in such dangerous conflicts.