1 Samuel 28:2

And David said to Anchus, Thus now thou shalt know what thy servant will do. And Anchus said to David, So will I make thee captain of my body-guard continually.

And David said to Achish, Surely thou shalt know what thy servant can do. And Achish said to David, Therefore will I make thee keeper of mine head for ever.

David said to Achish, “Therefore you will know what your servant can do.” Achish said to David, “Therefore I will make you my bodyguard forever.”