醫醫馬來 Go And Doctor The Horse
他跑將來，對行者說：「哥啊，且莫去醫皇帝，且快去醫醫馬來。那亡人乾結了，莫想尿得出一點兒。」行者笑道：「我和你去。」沙僧道：「我也去看看。」他跑将来，对行者说：「哥啊，且莫去医皇帝，且快去医医马来。那亡人干结了，莫想尿得出一点儿。」行者笑道：「我和你去。」沙僧道：「我也去看看。」
逐句解 Line by line
He came running back and said to Pilgrim, "Brother! Never mind doctoring the emperor — go and doctor the horse first.
醫醫馬 — go and doctor the horse — reverses the entire errand in three characters, and Eight Rules does not appear to notice he has said anything funny. 將 in 跑將來 is jiāng, the everyday word that pushes a verb along — "came running back".
"The wretched creature is all dried up. There is no hope of getting a single drop out of him."
亡人 is abuse, roughly "you dead thing", and he is using it of a dragon. 乾 is gān, dried out, not the qián of 乾坤, heaven and earth. 尿得出 takes the light de of possibility, and 兒 the light suffix.
Pilgrim laughed and said, "I will go with you."
和 is hé here, simply "with" — the same character will shortly mean stirring things together, and take a different reading for it.
Sha the monk said, "I shall come and have a look too."
And with that the entire party goes outside to watch a horse urinate.
The report back is the best line in the chapter. Never mind doctoring the emperor — go and doctor the horse. It reverses the entire errand in three characters, and Eight Rules gives no sign of noticing that he has said anything funny.
What follows is the whole party walking outside to watch a horse urinate. The chapter has been steering towards this since the golden threads, and it arrives with no change of tone whatever: Pilgrim laughs, Sha the monk says he will come and look, and the scene simply moves outdoors.