呆子先走 The Blockhead Bolts
八戒慌了道：「哥哥，不停當，這一鑽在火裡，莫想得活。把老豬弄做個燒熟的，加上香料，盡他受用哩。快走，快走。」說聲走，他也不顧行者，跑過澗去了。八戒慌了道：「哥哥，不停当，这一钻在火里，莫想得活。把老猪弄做个烧熟的，加上香料，尽他受用哩。快走，快走。」说声走，他也不顾行者，跑过涧去了。
逐句解 Line by line
Eight Rules panicked: ‘Brother, this is bad — plunge into that fire, and don't think to come out alive.
不停當 is the phrase from the demon's checklist two scenes ago, turned inside out: things are not in order. 當 keeps the same dàng sound. 莫想得活, do not even think about getting out alive, uses 得 at its full dé -- getting out is something you would have to achieve. Bajie has assessed the situation and reached a conclusion.
They'll turn old Pig into a roasted dish, add the spices, and let him feast to his heart's content.
The conclusion, and it is entirely about himself. Old Pig will be turned into a roast, spices added, and the demon will eat his fill. 盡他受用 means to let him have the full use of it. A note on the reading: the house rule for 盡 is jìn everywhere, on the grounds that when the sense is the permissive "let him have his fill," Chinese writes it with a different character, 儘. The 1592 edition prints 盡 here, and the reading follows the rule. Bajie, meanwhile, has got as far as imagining the seasoning.
Away, away!’
Two words, twice. There is no argument in this line and no attempt at one -- just a pig deciding to leave.
And with the word ‘go,’ heedless of the Pilgrim, he ran off across the torrent and was gone.
And he goes. 不顧行者, without a thought for the Pilgrim, and across the torrent. The 澗 is the Withered-Pine Torrent from the cave's full name, and it functions here as a boundary: on the far side of it Bajie feels safe. Wukong is still in the fire.
Bajie's desertion is played for comedy and it is genuinely funny -- the leap from "this looks bad" to a detailed vision of himself roasted and seasoned on the demon's table takes him about one sentence. Self-pity at that speed is a character trait, not a lapse.
It is also a real abandonment. He pronounces the case hopeless, shouts twice, and runs, leaving the Great Sage inside a fire that neither of them understands. The chapter title says 心猿遭火敗, the Mind-Ape suffers defeat by fire, and this is the moment the Mind-Ape is left alone with it.