咬響鋼牙 Grinding His Steel Teeth
牛王聞言，心如火發，咬響鋼牙罵道：「你說你不無禮，你原來是借扇之故。一定先欺我山妻，山妻想是不肯，故來尋我，且又趕我愛妾。常言道：『朋友妻，不可欺；朋友妾，不可滅。』你既欺我妻又滅我妾，多大無禮？上來吃我一棍。」牛王闻言，心如火发，咬响钢牙骂道：「你说你不无礼，你原来是借扇之故。一定先欺我山妻，山妻想是不肯，故来寻我，且又赶我爱妾。常言道：『朋友妻，不可欺；朋友妾，不可灭。』你既欺我妻又灭我妾，多大无礼？上来吃我一棍。」
逐句解 Line by line
Hearing this, the Bull King's heart flared as with fire. He ground his steel teeth till they rang, and railed, "You said you had done no discourtesy — and the whole cause of it turns out to be the borrowing of the fan!"
咬響 is to grind the teeth hard enough to be heard. 你不無禮 points back to the apology three passages ago: the Bull King now rereads the whole thing as groundwork for the request.
"Assuredly you first insulted my mountain wife; my mountain wife, I suppose, would not consent; and so you came seeking me, and chased my beloved concubine into the bargain."
一定 takes yí before the falling tone of 定. 山妻 is the humble form for one's own wife, used twice here. And the reconstruction he offers is entirely correct.
The common saying has it: the wife of a friend is not to be wronged; the concubine of a friend is not to be slighted.
A proverb, quoted in its own marks, and still current: a friend's wife is not to be wronged, a friend's concubine not to be slighted. The two halves are identical in build — 朋友 plus a person, 不可 plus a verb — with no escalation between them. Both instances of 不 take bù before the dipping tone of 可.
"You have wronged my wife and slighted my concubine both. How great an incivility is that? Come up and take a stroke of my staff!"
The proverb's two halves are applied in order, 欺 to the wife and 滅 to the concubine, so the charge arrives as a formal syllogism with the maxim as its major premise. 一棍 takes yí before the falling tone of 棍.
The Bull King's reasoning is sound, and that is what makes the passage work. He infers from the request that the courtesy preceding it was instrumental; he infers from the order of events that the Great Sage went to the Rākṣasī first, was refused, and came to him only as a fallback; and he infers that the pursuit of the Jade-Faced Princess was part of the same errand. Every inference is correct. We have watched each step.
The proverb is the hinge. Quoted as received wisdom, it supplies a general rule under which both grievances fall, and he applies it at once and in order — the wife wronged, the concubine slighted. What began as a domestic quarrel is thereby raised to a breach of the code between sworn brothers, which is the one ground on which he can strike a man he has just pardoned.
It is worth noting what the pardon was actually worth. Granted three passages ago on the strength of old acquaintance, it lasts exactly as long as the Great Sage refrains from asking for anything. The novel is precise about this: friendship among these figures is real, and it is also a currency, and the Great Sage has just spent his entire balance on a request that has not even been answered yet.