1 Samuel 18:7-9

7As they danced, they sang: “Saul has slain his thousands, and David his tens of thousands.” 8Saul was very angry; this refrain displeased him greatly. “They have credited David with tens of thousands,” he thought, “but me with only thousands. What more can he get but the kingdom?”

9And from that time on Saul kept a close eye on David.