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.

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

And David said to Achis: Now thou shalt know what thy servant will do. And Achis said to David: And I will appoint thee to guard my life for ever.

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

And David saith unto Achish, 'Therefore, thou dost know that which thy servant dost do.' And Achish saith unto David, 'Therefore, keeper of my head I do appoint thee all the days.'

And David said to Achish, Surely you shall know what your servant can do. And Achish said to David, Therefore will I make you keeper of my head for ever.

And David said to Achish, You will see now what your servant will do. And Achish said to David, Then I will make you keeper of my head for ever.

And David said to Achish, "You know now what your servant will do." And Achish said to David, "And so, I will appoint you to guard my head for all days."

Thou shalt know - David dissembled (compare also 1-Samuel 29:8), hoping, no doubt, that something would happen to prevent his fighting against his king and country.
Keeper of mine head - Captain of his bodyguard.

Surely thou shalt know what thy servant can do - This was another equivocal answer; and could only be understood by his succeeding conduct. It might imply what he could do in favor of the Philistines against Israel; or in favor of Israel against the Philistines. Achish understood it in the former sense; and therefore he said to David, I will make thee keeper of my head for ever; i.e., Thou shalt be captain of my life-guards.

And David said to Achish, surely thou shalt know what thy servant can do,.... By which he would have Achish understand, and so he did, that he would exert himself in favour of the Philistines, and against Israel, and do great and brave things, of which Achish would be, made sensible, through his heroic courage and valour; though he meant rather what he could and should do for Israel against the Philistines, if he had an opportunity: but it seems best of all to consider David as quite undetermined, and at a loss what to do, hoping that God in his providence would extricate him out of this difficulty, and direct him what he should do, which then Achish would know; and accordingly he was delivered out of it:
and Achish said to David: putting confidence in him on account of his answer, and believing he was hearty in engaging in the war with the Philistines against Israel:
therefore will I make thee keeper of mine head for ever; the captain of his bodyguard, which post he should hold for life; or he proposed to put him into this post, that he might be with him, near his person, and under his eye, that he might observe how he behaved himself; which may show some suspicion of him.

Surely thou shalt know what thy servant can do--This answer, while it seemed to express an apparent cheerfulness in agreeing to the proposal, contained a studied ambiguity--a wary and politic generality.
Therefore will I make thee keeper of mine head for ever--or, "my life"; that is, "captain of my bodyguard," an office of great trust and high honor.

Can do - He speaks ambiguously, as he did before.