1 Samuel 28:2

Surely thou shalt know. Hebrew, "Therefore thou shalt know," i.e. if the case be so, thou shalt know, etc. The rendering of the A.V. makes David repeat the words of Achish, which literally are, "knowing thou shalt know," the Hebrew way of making a strong affirmation. David's reply is really ambiguous, but is understood by Achish as a boastful assent, and he thereupon promises, Therefore will I make thee keeper of mine head, i.e. captain of my bodyguard, forever . Therefore is exactly the same word as that used by David, and has just the same meaning, namely, "If the case be so, if thou provest thy valour, then I, etc.

SAUL AND THE WITCH OF ENDOR ( 1 Samuel 28:3-25 ).