Jamieson, Fausset and Brown on Revelation 2:23

23. her children--(Is 57:3; Eze 23:45, 47). Her proper adherents; not those who suffer her, but those who are begotten of her. A distinct class from the last in Re 2:22 (compare Note, see on Re 2:22), whose sin was less direct, being that only of connivance.

kill ... with death--Compare the disaster that overtook the literal Jezebel's votaries of Baal, and Ahab's sons, 1Ki 18:40; 2Ki 10:6, 7, 24, 25. Kill with death is a Hebraism for slay with most sure and awful death; so "dying thou shalt die" (Ge 2:17). Not "die the common death of men" (Nu 16:29).

all the churches shall know--implying that these addresses are designed for the catholic Church of all ages and places. So palpably shall God's hand be seen in the judgment on Thyatira, that the whole Church shall recognize it as God's doing.

I am he--the "I" is strongly emphatical: "that it is I am He who," &c.

searcheth ... hearts--God's peculiar attribute is given to Christ. The "reins" are the seat of the desires; the "heart," that of the thoughts. The Greek for "searcheth" expresses an accurate following up of all tracks and windings.

unto every one of you--literally, "unto you, to each."

according to your works--to be judged not according to the mere act as it appears to man, but with reference to the motive, faith and love being the only motives which God recognizes as sound.