3510 GREEK νεφρος, NEPHROS nef-ros' of uncertain affinity; a kidney (plural), i.e. (figuratively) the inmost mind:--reins.
νεφρους Rev 2:23 And I will kill her children with death; and all the churches shall know that I am he which searcheth the reins and hearts: and I will give unto every one of you according to your works.