一向清廉 Clean-Handed, and Careless
行者暗笑道：「此是他大爺的神子。」卻就綽著經兒叫道：「坤三賢姪，你做官雖承祖廕，一向清廉，怎的昨日無知，把四個聖僧當賊，不審來音，囚於禁內？那獄神、土地、城隍不安，報與閻君，閻君差鬼使押我來對你說，教你推情察理，快快解放他；不然，就教你去陰司折證也。」行者暗笑道：「此是他大爷的神子。」却就绰着经儿叫道：「坤三贤姪，你做官虽承祖荫，一向清廉，怎的昨日无知，把四个圣僧当贼，不审来音，囚于禁内？那狱神、土地、城隍不安，报与阎君，阎君差鬼使押我来对你说，教你推情察理，快快解放他；不然，就教你去阴司折证也。」
逐句解 Line by line
Monkey laughed to himself. "So this is his great-uncle's spirit portrait." Then, putting on a solemn tone, he called out: "Kunsan, worthy nephew! You hold office on your forebears' merit and have been clean-handed all along — so how came you yesterday, in your ignorance, to take four holy monks for thieves, and lock them up in prison without hearing what they had to say?"
綽著經兒 — putting on a solemn tone. The phrase is a performer's one: taking up the manner, striking the attitude. Monkey is doing a voice again. 一向清廉 — clean-handed all along. Monkey concedes the point before he makes his accusation, and it is not flattery: the prefect has been honest and careful throughout, and the chapter has shown it. 不審來音 — without hearing what they had to say. This is the actual charge, and it is exact. The prefect did not take a bribe and did not rush to judgement; he simply did not investigate the account the accused gave him.
"The prison god, the earth god and the city god are unquiet over it, and have reported it to the king of the dead. He has dispatched a ghost-runner to escort me here to tell you: weigh the circumstances, look into the reason, and set them free at once."
差 — dispatched. The third of this chapter's seven uses in the send-somebody sense, and Monkey is now using the same invented chain of command he used on the Kou family four hundred characters ago: three local gods, a report upward, a warrant. 推情察理 — weigh the circumstances, look into the reason. Four characters of judicial advice, and they are the right advice. A ghost is telling a magistrate to do his job properly.
"If you do not, I am to have you brought down to the shades below to argue it out."
折證 — to be confronted and give evidence, in the underworld courts. It is a legal word, not a supernatural one: the shades below have hearings, and the threat is that the prefect will be a party at one. This chapter's underworld is a court system from top to bottom. Monkey has threatened a household with a haunting and a magistrate with litigation, and he has judged both audiences correctly.
Monkey's accusation is precise and it is fair. He does not say the prefect is corrupt — he says the opposite, that the man has been clean-handed all along. What he says is that the prefect locked four men up without hearing their account, and that is exactly what happened.
The threat is calibrated to the man. The Kou family got a haunting: a month of trouble in the house, nobody left alive, the fowls and dogs included. The prefect gets a summons. He is told he will be brought down to argue his case in the courts of the dead, which for a career official is a much more frightening prospect than a ghost in the hall.
And the advice inside the threat is good law. Weigh the circumstances, look into the reason — it is what he should have done with the travel warrant when Tripitaka held it out in open court. The chapter has arranged for a monkey impersonating a dead uncle to be the one who says so.