Strictly speaking, it isn’t just the term “kings” (since God’s people are called kings and priests previously in RevJohn, for example), but the phrase “kings of the earth”, which God’s people are never called previously in RevJohn. Obviously they’re God’s people in chapter 21, but they weren’t previously.
Oh, looking back over the thread I see this is one of those I somehow never got around to. [tag]WE ARE ALL BROTHERS[/tag] did a great job! That Zeph 3 reference was trumpy, too, [tag]redhotmagma[/tag].
Having caught up on the thread, I think the only spare from BAaron’s (Revival’s) original post was Rev 1:5-6. Contextually the point seems clear enough: the pagan kings of the earth (even the ones oppressing the church in the day of John) aren’t the real kings, Jesus is, and He’s king over them, too, even though they don’t acknowledge Him (being rebel kings). That’s a pretty standard claim throughout the OT (with Jesus == God), and certainly fits the rest of RevJohn up until Rev 21, which as WAAB pointed out references Isaiah 60 heavily (among a couple other scriptures) to indicate those are previously rebel kings now repenting and coming in.
Moreover, those who are faithful now are coming into the kingdom of Christ to be priests; and later also to become kings as well as priests. But those who are already faithful aren’t called “kings of the earth” either here or later in RevJohn. Even at Rev 21, the kings of the earth weren’t already faithful (per backreference to Isaiah 60), though they’re certainly faithful and repentant of their sins now (or they wouldn’t be able to enter the NJ where none may come whose name isn’t written in the book of life.)
The detail a couple of verses later in chapter 1, where all the tribes of the earth, even those who pierced Him, will see Jesus and mourn, might or might not be construed as penitent mourning. It certainly means that in Zech 12:10, when YHWH arrives to defend Israel from her final siege, defeating her enemies and sending the (or a) spirit of grace and supplication so that those who had survived the battle up until then will mourn over Him Whom they had pierced as they would over a firstborn son. But God had sent that final battle against them because they had been impenitent sinners up until then; it is only when they see YHWH personally descending to rescue them at last they they repent, and mourn instead of rejoicing – but God isn’t coming to destroy them but to save them.
That isn’t “all the tribes of the earth” at that time, only the survivors of Jerusalem. But Rev 1:7 combines the theme and language of Matt 24:30 (including reference to the arrival of the Son of Man to take the throne of the Ancient of Days from Daniel) with Zech 12:10, and the combination is suggestive that all the tribes of the earth will be mourning like the ones who pierced YHWH, due to YHWH pouring out the spirit of grace and supplication. That wouldn’t necessarily have to happen all at once, if there are details indicating it doesn’t, and also details indicating it happens to everyone eventually. (Which there are, and there are. Zeph 3:8-9 being one pertinent example.)