A.T. Robertson Commentary Revelation 2:23

"And I will kill her children with death; and all the churches shall know that I am he that searcheth the reins and hearts: and I will give unto each one of you according to your works." — Revelation 2:23 (ASV)

I will kill with death (αποκτενω εν θανατω). Future (volitive) active of αποκτεινω with the tautological (cognate) εν θανατω (in the sense of pestilence) as in Eze 33:27.

Her children (τα τεκνα αυτης). Either her actual children, like the fate of Ahab's sons (2 Kings 10:7) or "her spiritual progeny" (Swete) who have completely accepted her Nicolaitan practices.

Shall know (γνωσοντα). Future (ingressive punctiliar) middle of γινωσκω, "shall come to know." "The doom of the offenders was to be known as widely as the scandal had been" (Charles).

Searcheth (εραυνων). Present active articular participle of εραυναω, to follow up, to track out, late form for ερευναω, from Jer 17:10.

Reins (νεφρους). Old word for kidneys, here only in N.T., quoted also with καρδιας from Jer 17:10. See 22:17 for the reward of punishment.