不明之事 A Thing I Do Not Understand
少頃，安排停當，驛丞即請四眾同吃了齋供。又教手下人打掃客房安歇。三藏感謝不盡。既坐下，長老道：「貧僧有一件不明之事請教，煩為指示。少顷，安排停当，驿丞即请四众同吃了斋供。又教手下人打扫客房安歇。三藏感谢不尽。既坐下，长老道：「贫僧有一件不明之事请教，烦为指示。
逐句解 Line by line
Before long everything was ready, and the courier chief invited the four of them to take the vegetarian meal together.
停當 takes 當 as dàng, not dāng — in this compound it means settled and in order, and the character goes to the falling tone whenever it has been fixed into a word like this. 齋供 zhāi gòng is food prepared under monastic rules: no meat, no strong-smelling vegetables.
He also told his people to sweep out a guest room for them to rest in.
The courier chief is doing his job properly, and will go on doing it properly right up to the moment he has to decide whether to tell the truth.
Tripitaka thanked him without ceasing.
Six characters. 不 is bú, lifted to the rising tone because 盡 beside it takes the falling jìn — the same pairing as 看不盡 in the market a few passages back.
When they had sat down the elder said, "This poor monk has a thing he does not understand and would ask about; be so good as to instruct me.
Tripitaka approaches it very carefully, and the politeness is doing work: he is about to ask an official of a foreign court about something he has been told twice already to leave alone. 為 is wèi here, on my behalf, and not the copular wéi.
The chapter has been building to this conversation for eight hundred characters and it opens it with supper. Everything in the scene is comfortable — a hot meal, a swept room, thanks given and accepted — and the discomfort has to be introduced by the guest.
Tripitaka is the one who asks. It is worth registering, because he is not usually the one who does anything. Wukong has already looked in the coops and reported; Bajie has already produced a comfortable explanation; and it is the master, the least practical member of the party, who cannot let it go.