熟鐵之腿 Legs of Wrought Iron
大仙笑道：「這潑猴倒言語膂烈。這等便先打他。」小仙問：「打多少？」大仙道：「照依果數，打三十鞭。」那小仙掄鞭就打。行者恐仙家法大，睜圓眼瞅定，看他打那裡。原來打腿，行者就把腰扭一扭，叫聲：「變！」變作兩條熟鐵腿，看他怎麼打。那小仙一下一下的打了三十，天早向午了。大仙笑道：「这泼猴倒言语膂烈。这等便先打他。」小仙问：「打多少？」大仙道：「照依果数，打三十鞭。」那小仙抡鞭就打。行者恐仙家法大，睁圆眼瞅定，看他打那里。原来打腿，行者就把腰扭一扭，叫声：「变！」变作两条熟铁腿，看他怎么打。那小仙一下一下的打了三十，天早向午了。
逐句解 Line by line
The Great Immortal laughed: "This brazen monkey is bold enough in his talk.
膂烈, lǚ liè, is forceful, full-blooded — 膂 is the spine, so the sense is speech with a backbone in it. 倒 is dào, "actually, if anything": the immortal is surprised into approval.
"In that case, beat him first."
Permission granted, and the sentence redirected in five words.
The little immortal asked, "How many strokes?"
The executioner asks for a number, as executioners do.
The Great Immortal said, "By the number of the fruit—thirty lashes."
And here is the arithmetic of the punishment. 照依果數, zhào yī guǒ shù, "according to the number of the fruits," with 數 as the noun shù. The tree bore thirty fruits in ten thousand years — that is the whole yield of a tree older than the world — so thirty lashes is one stroke for every fruit that tree would ever have produced, not one for each of the four that were stolen. The sentence is calculated on the loss, not the theft.
That little immortal swung the whip and struck.
掄鞭就打, swung the whip and struck — no ceremony at all.
The Pilgrim, fearing the immortal's magic ran deep, glared round-eyed and fixed his gaze to see where he would strike.
He is not being brave, he is being careful. 恐仙家法大, "fearing the immortal's arts ran deep" — he has already been bagged in a sleeve today and is taking nothing on trust. 瞅定, chǒu dìng, is fixing your eyes on something and not letting go.
It turned out he struck the legs; so the Pilgrim gave his waist a twist and cried, "Change!"
Legs. Good — that he can work with. 把腰扭一扭, a twist of the waist, is all the preparation a transformation needs.
and turned them into two legs of wrought iron—to see how he would beat those.
熟鐵, shú tiě, is wrought iron: the soft, worked, malleable kind that takes a beating without cracking. Not a random choice of metal.
That little immortal laid on thirty strokes, one after another, and the day was already near noon.
一下一下的打了三十, thirty strokes, one after another, and the morning gone with them — 天早向午了, the day already turning toward noon. The flat arithmetic of the sentence is the joke: he is counting carefully, and it is all landing on iron.
Wukong takes the beating and cheats it, and the chapter lets both things be true at once. He genuinely spares his master; he also turns his legs to wrought iron before the first stroke lands, so the courage costs him nothing. Heroism and trickery in the same gesture, which is the most accurate short description of this character anyone has managed.
The detail worth catching is the arithmetic. 照依果數 — thirty lashes, by the number of the fruits — and the tree bore thirty fruits in ten thousand years. He is not being fined for the four he stole; he is being charged for the entire output of the tree, because there will not be any more. The Great Immortal has done his sums, and they are the sums of a man who has lost something irreplaceable.
And the choice of iron is a small joke of its own. Wrought iron is the soft, worked kind that absorbs a hammering without breaking, which is precisely what is wanted. Even the monkey's cheating is well researched.