窮寇勿追 Do Not Pursue A Desperate Foe
八戒便要趕去，行者止住道：「且莫趕他，正是『窮寇勿追』。他被細犬咬了頭，必定是多死少生。等我變做他的模樣，你分開水路，趕我進去，尋那公主，詐他寶貝來也。」八戒便要赶去，行者止住道：「且莫赶他，正是『穷寇勿追』。他被细犬咬了头，必定是多死少生。等我变做他的模样，你分开水路，赶我进去，寻那公主，诈他宝贝来也。」
逐句解 Line by line
Eight Rules was for going after it, but Pilgrim stopped him: "Do not chase him. As the saying has it, do not pursue a desperate foe.
No graph in this segment stands in any guard roster. 窮寇勿追 is a maxim of the military writers, printed here inside its own quotation marks — the third saying quoted as an authority in this chapter, after 武不善作 and 征不待時 — and all three are about war.
With his head bitten off by the hound, he is a great deal more likely dead than alive.
少 is shǎo, few, and 多死少生 weighs the two outcomes against each other by quantity — much death and little life — rather than stating a probability. 了 is the perfective le.
Let me change into his shape; you part the water and drive me in, and I will find the princess and get the treasure out of her by a trick."
模樣 takes 模 at mú, the vernacular compound the corpus holds by explicit registration, where the same graph took mó at 身模 and 規模 earlier in the chapter. 分 is fēn and 的 holds de. 詐 is to obtain by deceiving, and Pilgrim names the method plainly.
Pilgrim stops the pursuit with a maxim, which is now the third time in this chapter that a saying has been produced to settle a question. The fiend used one before the first fight, Erlang used one to argue for attacking at night, and Pilgrim uses one here to argue for not attacking at all. All three are about war, and each one is used to get its speaker what he already wanted.
The reasoning underneath it is practical rather than merciful. He is not sparing the creature; he is observing that a thing with a head bitten off is probably dying anyway, and that there is something more useful to do with the time.
That something is a second disguise. Having spent the middle of the chapter as a crab, he now proposes to go in as the son-in-law himself, and the plan he describes ends in the word 詐 — to swindle. Nobody objects, and nobody points out that the treasure could simply be searched for.