積功累德 Merit Not Gold
行者聽說，滿面喜生，呵呵的笑道：「莫說，莫說。若說千金為謝，半點甘雨全無；但論積功累德，老孫送你一場大雨。」行者听说，满面喜生，呵呵的笑道：「莫说，莫说。若说千金为谢，半点甘雨全无；但论积功累德，老孙送你一场大雨。」
逐句解 Line by line
Pilgrim heard him out, and delight spread over his whole face. He laughed aloud. "Say no more, say no more.
呵呵 is the laugh — and worth flagging, because a character two passages away that looks as though it might be laughter is not. This is the chapter's only real one. 滿面喜生, joy rising all over the face, is a stock phrase and a peculiar reaction to a report of mass starvation; what has delighted him is the opportunity.
"If you talk of a thousand in gold by way of thanks, you will not get half a drop of sweet rain.
為 is wéi here, meaning to serve as — a thousand in gold taken as thanks. An identical construction elsewhere in the novel settles the reading, where lotus root serves as bones and lotus leaves serve as clothing. 半點, half a drop, is still the ordinary Chinese way of saying not the slightest bit.
"But talk of piling up merit and accumulating virtue, and Old Monkey will send you a great rain."
場 is cháng, the measure word for something that runs its course and ends — a bout of rain. Read chǎng the same character would mean a place. 積功累德, heaping up merit and piling up virtue, is the vocabulary of the moral ledger that both Buddhism and Daoism keep, and Pilgrim has just changed the currency of the negotiation.
Here is the chapter's hinge, and it takes three lines. Offer money and you get nothing. Offer merit and you get rain.
Pilgrim is not being high-minded for the sake of it, and he is not haggling. He is stating what will turn out to be the literal mechanics of the situation: the rain has been withheld by heaven for a moral reason, and no sum of money can move it, because money is not the thing that is missing. He does not know this yet. He simply has the right instinct about what heaven responds to.
It is also, for those keeping track, a considerable piece of character development. The monkey who once ransacked heaven for a better job title is now refusing a thousand in gold and lecturing a provincial official about virtue — and doing it with a grin all over his face.