不分好歹 Cut Her Down and Save Her
沙僧真個回轉舊處，牽了馬，挑了擔，至跟前叫：「師父，怎麼說？」唐僧用手指定那樹上，叫：「八戒，解下那女菩薩來，救他一命。」獃子不分好歹，就去動手。沙僧真个回转旧处，牵了马，挑了担，至跟前叫：「师父，怎么说？」唐僧用手指定那树上，叫：「八戒，解下那女菩萨来，救他一命。」呆子不分好歹，就去动手。
逐句解 Line by line
Sha Monk did indeed go back to where they had been, led out the horse, shouldered the load, and came up saying, "Master, what is it?"
The 擔 is dàn, the load itself — the same baggage Bajie was handed at the foot of the mountain, back on Sha Monk's shoulder again without a word about it.
The Tang Monk pointed up at the tree and said, "Bajie, cut that Lady Bodhisattva down and save her life."
He is still calling her a bodhisattva, and he now says it as an instruction to somebody else. The courtesy has become an official description.
The Idiot, without stopping to sort good from bad, went straight to work.
不分好歹 — not telling good from bad — is still current Chinese for acting without judging the situation, and it is aimed squarely at Bajie here. It is also, in a chapter about a monk who cannot tell a demon from a girl, a phrase with more than one target.
The order is given and obeyed in a single breath. Tripitaka has heard one speech, asked no follow-up question, and is now directing a rescue.
The phrase about not sorting good from bad is thrown at Bajie, who is being blamed for doing as he is told. That is a little unfair, and the unfairness is the point: the person who has genuinely failed to sort good from bad is the one giving the instruction.
The chapter has been building to this since the pine-wood rhapsody warned about old foxes dressed as pretty women. Bajie has his hands on the ropes. What stops him is going to arrive from the sky, at speed, and be extremely unwelcome.