進退兩難 Caught Between Going and Staying
正是那進退兩難心問口，三思忍耐口問心。正自狐疑，那怪又叫一聲：「長老。」唐僧沒奈何，應他一聲道：「娘子，有。」正是那进退两难心问口，三思忍耐口问心。正自狐疑，那怪又叫一声：「长老。」唐僧没奈何，应他一声道：「娘子，有。」
逐句解 Line by line
This was truly the case of advance and retreat both hard, the heart asking the mouth, and three turns of thought and patience, the mouth asking the heart.
進退兩難 is a set four-character phrase still in daily use — advance is hard and retreat is hard, the exact English of caught between a rock and a hard place. 三思, to think three times, is equally alive: it is the standard advice to consider before acting. The teller has taken two ordinary sayings and locked them into a mirrored pair, heart asking mouth and mouth asking heart.
While he was still in two minds, the fiend called out once more: "Elder!"
狐疑 is fox-doubt, and the etymology is worth having: foxes were said to cross river ice in tiny stages, stopping to listen for cracking, so the word came to mean hesitating suspicion. It has meant that for two thousand years.
The Tang Monk had no help for it, and answered her once: "Madam. Here."
Two characters of reply, and the chapter turns on them. Once more 應 is yìng, to answer. 娘子 is the ordinary polite address to a woman and also what a man calls his wife — which is precisely the ambiguity Tripitaka has just stepped into.
The mirrored line about the heart asking the mouth is the sort of formula that survives because it is easy to say and hard to improve. A performer could land it, an audience could repeat it, and it describes indecision better than a paragraph would.
The fox on the ice is a genuinely old image. The character for doubt in this compound carries it, and Chinese has kept the fox as the animal of hesitation and suspicion ever since — which is a small irony here, given what the creature upstairs turns out to be.
And then he answers. Two characters, and every vow he swore a few passages ago is now under pressure, because the word he has used to her is the word a husband uses.