Read 1 Samuel 28:2 Using Other Translations
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, "Very well, you shall know what your servant can do." And Achish said to David, "Very well, I will make you my bodyguard for life."
“Very well!” David agreed. “Now you will see for yourself what we can do.” Then Achish told David, “I will make you my personal bodyguard for life.”