偷了金睛 Better to Steal the Beast
心中暗想道：「這牛王在此貪杯，那裡等得他散？就是散了，也不肯借扇與我。不如偷了他的金睛獸，變做牛魔王，去哄那羅剎女，騙他扇子，送我師父過山為妙。」心中暗想道：「这牛王在此贪杯，那里等得他散？就是散了，也不肯借扇与我。不如偷了他的金睛兽，变做牛魔王，去哄那罗刹女，骗他扇子，送我师父过山为妙。」
逐句解 Line by line
He thought within himself: "This Bull King is here greedy for his cup. How is one to wait until they break up?"
那裡 is rhetorical here — where is the waiting in that? — so 那 is nǎ. 等得 is the can-do shape with the toneless de. 散 is sàn, of a gathering breaking up.
"And even when they have broken up, he will not be willing to lend me the fan."
The second thought disposes of patience as a strategy: waiting would only be worth doing if the outcome of waiting were different, and it is not.
"Better to steal his golden-eyed beast, change into the Bull Demon King, go and hoodwink that Rākṣasī, cheat her out of the fan, and see my master over the mountain. That would be best."
為 is wéi in 為妙, the copular reading. 剎 is chà. The plan is stated in five verbs, and the whole remainder of the chapter carries them out in order.
The thinking-aloud is built as a syllogism and takes three steps to reach a plan. Waiting is impractical, because the Bull King is settled in for the evening; waiting is pointless, because he would refuse anyway; therefore the thing to do is impersonate him. Each step eliminates an option, and the conclusion arrives with the force of something deduced rather than invented.
What makes the plan work is that every element of it is already lying about. The beast is tethered where he was told to wait. The Bull King is inside and will be for hours. The Rākṣasī has never met the Jade-Faced Princess and has no way of checking a husband's story. The Great Sage has spent this chapter being outmanoeuvred; this is the first moment he is ahead of the situation, and it is because the situation handed him everything.
There is a symmetry the novel never points out. The Bull King left the Banana-Leaf Cave for another woman and rode to this pool on the golden-eyed beast. The Great Sage is about to ride that same beast back to the abandoned wife, wearing the husband's face. The animal that carried the desertion will now carry the deception.