If this is the scene in the Lotus Pier ancestral hall, it's chapters 87 and 88.
I gather that neither JC or LZ say "piss off," in the novel, but if it's just a translation option, it was LZ who probably said it.
Lol, and for the post title and commentary, in the novel, at first JC was telling WWX to leave. Then JC was trying to get them to stay when he realized WWX was hurt.
The scene in the novel is roughly:
WWX was going around Lotus Pier, intentionally keeping away from JC, and secretly taking LZ around to show him memory filled areas.
He takes LZ to burn incense at the ancestral hall, and in his heart secretly does part of a marriage ceremony with LZ. Wen Ning was outside Lotus Pier too.
JC had gone looking for WWX.
He saw WWX and LZ hugging under a tree, and is really shocked, processing how out of character that seemed for both WWX and LZ. He follows them to the ancestral hall, and seeing them in the ancestral hall makes him rage filled enough to forget being shocked and pretty much anything else.
JC likely sees WWX and LZ bowing in together (marriage ceremony style apparently) and laughs to announce himself.
He starts in on WWX for coming and going around Lotus Pier however he wants. For burning incense for the dead as if he's still a sect member, even bringing two unwelcome people.
WWX wants to defend LZ, and tells JC to be respectful in front of the dead, to be like a sect leader and to have discipline.
JC flares hard, and tells WWX he's the one who needs to stop acting shamelessly in the ancestral hall. Says to go hug and fool around with LZ somewhere else, away from Lotus Pier, away from him.
WWX gets freaked out, because as they talk, the more WWX denies that he and LZ are together, that they're really just friends, the more upset LZ seems to get.
WWX eventually tells JC to shut up and apologize to LZ, or he'll beat up JC.
JC scoffs and doubles down on them definitely being more than just friends. Says he's never seen friends like that.
WWX shouts "have you had enough yet?" and hits JC with an exploding talisman, making JC bloody and stagger from the impact.
JC brings out zidian, and it turns into a fight with WWX & LZ against JC. WWX dodges a couple times, but quickly realizes how messed up having a fight in the ancestral hall is given the context, and physically overloads from stress.
JC and LZ both notice, and stop fighting to try to see what's going on. WWX tells "Lan Zhan... let's go."
So LZ is going to leave with the WWX.
JC wants to stop them from going when he realizes WWX is really hurt, WWX isn't faking the way he used to in the past.
JC shouts at them "Stop!"
LZ replies "Leave!" (I'm gathering this is the line that is translated to "Piss off!" in the live action version? Context seems right.)
When LZ shouts, he also attacks JC again with bichen.
JC lashes back with zidian. Zidian starts overpowering bichen though, because JC is still holding zidian, while bichen was not in LZ's hand at that point.
Wen Ning arrives and takes the hit from zidian that JC was trying to pull back (the novel says JC didn't want to really hit LZ).
Then WN explains what went down with the golden core on WWX side.
So yeah. I get the impression that this scene is probably substantially different in the two versions?