坐著念經 Seated and Reciting
八戒、沙僧謹依使令，三個人都在堂下。郡侯焚香禮拜。三藏坐著念經。八戒、沙僧谨依使令，三个人都在堂下。郡侯焚香礼拜。三藏坐着念经。
逐句解 Line by line
Bajie and Sha Monk carefully did as they were told, and the three of them stood together below the hall.
謹依使令, respectfully following the order given, is formal language for two disciples arranging themselves in a courtyard. The novel is enjoying the ceremony of it.
The prefect burned incense and made his obeisance.
The same four characters that introduced him, almost — burning incense, bowing. He was doing this alone in his office when the news arrived, and he is doing it again now with everyone watching. Nothing about the man has changed except that he now has company.
Tripitaka sat and recited scripture.
著 is neutral zhe a final time in this stretch, joining the sitting to the reciting: seated and reciting, both going on at once. Five characters, and the scene is set.
The passage arranges everybody and then stops. Three disciples in the courtyard, the prefect at his incense, the master seated and reciting. It is staged like the opening of a ceremony, because that is what it is.
What follows in the next stretch is the part Pilgrim has been looking forward to — a dragon summoned out of a clear sky in front of witnesses. What he does not know, and what the reader will find out at the same moment he does, is that the dragon is going to turn him down on procedural grounds. The most confident man in the courtyard is about to be told he needs the correct paperwork.