些兒筋節 “Some Substance to Him”
國王在上聽見，心中暗喜道：「那小和尚說話，倒有些筋節。」沙僧聽見，暗笑道：「不知他一肚子筋節，還不曾拿出來哩。」大仙道：「不消講，陛下自然知之。」国王在上听见，心中暗喜道：「那小和尚说话，倒有些筋节。」沙僧听见，暗笑道：「不知他一肚子筋节，还不曾拿出来哩。」大仙道：「不消讲，陛下自然知之。」
逐句解 Line by line
The king, listening up above, was secretly pleased and said to himself, “That little monk, in what he says, actually has some substance to him.”
心中: 中 = zhōng. 那小和尚: 那 = nà. 倒有些: 倒 = dào, "actually, rather," with a note of surprise. 筋節 "sinew and joint" -- said of an argument, it means there is something firm inside it, much as English says a case has backbone.
Friar Sand, hearing it, laughed to himself, “Little do they know he has a whole bellyful of such tricks he has not yet brought out.”
一肚子: 肚 = dù, belly, not dǔ, which is tripe on a plate; the falling tone then pulls 一 to yí. 子 = zi, the light ending. 還不曾: 還 = hái. 哩 = li at the end of the sentence. Friar Sand is playing on the king's word: 筋節 meant "substance," and he turns it into a bellyful of the stuff.
The immortal said, “There is no need to declare anything — His Majesty will know of himself.”
不消講: 不 = bù, "no need to explain." 自然知之 "will know it of himself." Famous last words.
Three reactions to the same exchange. The king is impressed despite himself. Friar Sand is enjoying himself enormously. The immortal cannot be bothered.
Sand's aside is a wink over the reader's shoulder -- a whole bellyful of tricks he has not brought out yet -- and it is also a small pun, since he takes the king's word for shrewdness and measures it by the stomachful. The immortal's shrug, meanwhile, is the last confident thing he says in this chapter.