不中吃 He Is Not Good Eating
老魔道：「被我一口吞在腹中哩。」第三個魔頭大驚道：「大哥啊，我就不曾吩咐你，孫行者不中吃。」那大聖在肚裡道：「忒中吃，又禁饑，再不得餓。」老魔道：「被我一口吞在腹中哩。」第三个魔头大惊道：「大哥啊，我就不曾吩咐你，孙行者不中吃。」那大圣在肚里道：「忒中吃，又禁饥，再不得饿。」
逐句解 Line by line
The old fiend said, "I swallowed him down into my belly at a mouthful."
中 is plain zhōng, inside — and it is about to appear twice more in two characters with a different reading altogether.
The third demon chief was appalled: "Elder brother! I never got round to telling you — Sun Wukong is not good eating."
中 here is zhòng, the fit-for band: 不中吃 is not fit to eat, not good eating. That raising also drags the tone of 不 up to bú — the shift always runs that way before a falling tone. 吩咐 ends on a light 咐, one of a small set of everyday compounds whose second syllable has gone unstressed.
The Great Sage said from inside the belly, "Extremely good eating — and it staves off hunger too. You will never go hungry again."
中 is zhòng again, and this line is what settles the reading: 忒中吃, exceedingly good eating, answering 不中吃 word for word. 禁 is jīn, to withstand — it holds off hunger. 得 keeps the full dé after 再不, meaning "never again."
This is the funniest exchange in the chapter and the whole thing turns on a product review. The third chief warns that the prisoner is not good eating; the prisoner, from inside, disagrees and adds a nutritional claim.
It is also the site the opening scan of this chapter was most concerned with. The character 中 normally reads zhōng, in the middle of, and it does so six times in this part of the chapter alone — including in the sentence immediately before. Here and in the reply it is the other reading entirely, and the two sit twelve characters apart.