Rev Revelation, chapter Revelation of Jesus Christ, chapter 2
Behold, I will cast her into a bed, and them that commit adultery with her into great tribulation, except they repent of their deeds.
And I will kill her children with death; and all the churches shall know that I am he which searches the reins (literally, kidneys; figuratively, seat of emotion) and hearts: and I will give unto every one of you according to your works.1Sa 16:7; Psa 7:9; Jer 11:20; Jer 17:10