你那裡知道 You Have No Idea
行者三人在留春亭亦盡受用，各飲了幾杯，也都有些酣意。正欲去尋長老，只見長老已同國王在一閣。八戒獃性發作，應聲叫道：「好快活，好自在，今日也受用這一下了。卻該趁飽兒睡覺去也。」沙僧笑道：「二哥忒沒修養。這氣飽飫，如何睡覺？」八戒道：「你那裡知道，俗語云：『吃了飯兒不挺屍，肚裡沒板脂』哩。」行者三人在留春亭亦尽受用，各饮了几杯，也都有些酣意。正欲去寻长老，只见长老已同国王在一阁。八戒呆性发作，应声叫道：「好快活，好自在，今日也受用这一下了。却该趁饱儿睡觉去也。」沙僧笑道：「二哥忒没修养。这气饱饫，如何睡觉？」八戒道：「你那里知道，俗语云：『吃了饭儿不挺尸，肚里没板脂』哩。」
逐句解 Line by line
Pilgrim and the other two had enjoyed themselves thoroughly in the Spring-Keeping Pavilion as well, and having drunk several cups apiece they were all somewhat merry. They were just about to go and look for the elder when they saw that he was already with the king up in the other pavilion.
The chapter cuts to the far table, and the three of them have had a good afternoon. Note the small failure of the plan. They went to look for their master and found him seated with the king, unreachable across a garden. Pilgrim has not laid eyes on the princess and the twelfth is coming.
Eight Rules's foolish streak came out and he called out in answer, "How pleasant! How comfortable! We have had a good time of it today. Now we ought to go and sleep on a full belly."
睡覺 is to sleep, so 覺 is jiào here — not the jué of waking or noticing, which is what the same character does at seven other places in this chapter. The word for sleeping is built out of the word for waking up, which is a joke Chinese has been making without noticing for a very long time.
Sha Monk laughed and said, "Second brother, you have no self-discipline at all. With your wind that full, how are you going to sleep?"
Sha Monk barely speaks in this chapter and both times he does it is to take Eight Rules down a peg. 氣飽飫 is being gorged to the point of wind — the physical complaint, stated plainly, in the middle of a chapter otherwise full of jade liquor and auspicious snow.
Eight Rules said, "You have no idea. As the common saying goes, 'Eat your rice and don't flop down like a corpse, or there'll be no fat on your gut.'"
你那裡知道 — you have no idea — is a set brush-off, and the 那 in it is nǎ, the questioning one, not the nà that points at something. It is asking from where would you know, and expecting no answer. All six times the novel uses it, somebody is telling somebody else they are out of their depth: four of them are Pilgrim and the other two are Eight Rules. The proverb sits in the inner brackets the edition keeps for a citation, and it is as coarse as it looks: 挺屍 is to lay yourself out like a corpse, and 板脂 is slab fat. Eight Rules is claiming, with a straight face and a folk saying, that lying down after dinner is bad for you.
A comic breather between the poetry and the beating, and it works by scale. The last passage had four poems answered rhyme for rhyme in front of a king. This one has three monks slightly drunk arguing about whether you should lie down after a big meal.
The joke about Eight Rules is never that he is stupid. It is that he applies real learning to the wrong subject. He has quoted a genuine proverb, correctly, in support of his position — he simply happens to be the one member of the party for whom the position is indefensible.
And the plot is quietly not advancing. Pilgrim promised to watch the princess bow to her parents; he is instead at a separate table with a tipsy pig, watching his master across a garden. Two of the four days are gone.