雷公爺爺 "Lord Thunder!"
此時卻驚動那寺裡大小僧人、上下房長老，聽得鐘聲亂響，一齊擁出道：「那個野人在這裡亂敲鐘鼓？」行者跳將出來，咄的一聲道：「是你孫外公撞了耍子的。」那些和尚一見了，諕得跌跌滾滾，都爬在地下道：「雷公爺爺！」行者道：「雷公是我的重孫兒哩。起來，起來，不要怕，我們是東土大唐來的老爺。」眾僧方才禮拜。見了三藏，都才放心不怕。內有本寺院主請道：「老爺們到後方丈中奉茶。」遂而解韁牽馬，擡了行李，轉過正殿，徑入後房，序了坐次。此时却惊动那寺里大小僧人、上下房长老，听得钟声乱响，一齐拥出道：「那个野人在这里乱敲钟鼓？」行者跳将出来，咄的一声道：「是你孙外公撞了耍子的。」那些和尚一见了，諕得跌跌滚滚，都爬在地下道：「雷公爷爷！」行者道：「雷公是我的重孙儿哩。起来，起来，不要怕，我们是东土大唐来的老爷。」众僧方才礼拜。见了三藏，都才放心不怕。内有本寺院主请道：「老爷们到后方丈中奉茶。」遂而解缰牵马，擡了行李，转过正殿，径入后房，序了坐次。
逐句解 Line by line
By now the din had roused every monk of the temple, great and small, and the elders of the upper and lower quarters; hearing the bell clanging wildly, they came crowding out together and cried,
上下房 are the ranked residences of a large monastery, and the phrase quietly establishes that this is a populous house — later we learn it holds some two hundred and thirty souls. 聽得 takes the neutral de, a complement of manner.
"What wild man is banging away at the bell and drum in here?"
那個 is interrogative, nǎ ge, "which, what." 野人 is not yet an insult aimed at Wukong in particular — the monks cannot see who is ringing — but the word will fit him remarkably well.
The Pilgrim came springing out and barked at them, "It was your Grandpa Sun, ringing it for sport."
跳將出來: 將 (jiāng) is the empty verbal infix of Ming vernacular, lending force and suddenness to the motion. 孫外公, "your maternal grandsire Sun," is Wukong's standing insolence — a claim of seniority in the same breath as his surname. 耍子 ("for play") takes the neutral zi.
At the sight of him the monks were so terrified that they stumbled and rolled, and every one of them crawled upon the ground, crying, "Lord Thunder! Grandfather!"
諕 (U+8AD5) is a variant of 嚇 and reads xià; 諕得 takes de. 跌跌滾滾, "tripping and tumbling." 雷公 is the Duke of Thunder, whose temple image has a beaked, simian face and a mallet — a resemblance the novel exploits more than once.
The Pilgrim said, "Lord Thunder is my own great-grandson. Get up, get up, don't be frightened. We are gentlemen come from the Great Tang in the Land of the East."
重孫兒 is a great-grandson. The boast turns the monks' terror inside out: they have mistaken him for a god, and he replies that the god is three generations his junior. From the creature who broke Heaven's gates it is not, strictly, a lie.
Only then did the assembly of monks make their bows. When they saw Sanzang, they were all at last easy and unafraid.
The paired 方才 and 都才 ("only then… only then") measure how slowly the fright drains away. It is the sight of Sanzang, not the words of Wukong, that steadies them: the human face reassures where the true power does not.
Among them the prior of the monastery invited them: "Let the reverend gentlemen come to the abbot's quarters at the rear and take tea."
院主 (yuànzhǔ) is the prior, the officer who administers the house beneath the abbot. He speaks here as the voice of hospitality; he will speak later as the voice of arithmetic.
So they loosed the halter and led the horse, took up the baggage, passed round the main hall, went straight into the rear chambers, and seated themselves in order of precedence.
韁 (jiāng) is the halter-rope. 序了坐次 — "arranged the order of the seats" — is a Confucian ritual of precedence performed inside a Buddhist cloister, and nobody in the scene finds this remarkable. The novel's three teachings are never so much reconciled as simply, unreflectingly, lived at once.
The monks of the Guanyin cloister meet the Great Sage exactly as the celestial bureaucracy once did: they fall down. But where Heaven fell down before power, these men fall down before a face. They take Wukong for 雷公, the Duke of Thunder — the one god in the pantheon who looks like a monkey — and they grovel to an image, which is what this monastery, for all its samādhi and its prajñā, has been trained to do. Wukong's reply is a jest and a genealogy at once: Lord Thunder is his great-grandson. The monks who worship the Thunder God are prostrate before someone who outranks him, and they cannot tell.
What finally calms them is not the boast but Sanzang: 見了三藏，都才放心不怕. The scene thus completes the pattern the chapter has been drawing since its opening 賦 — this is a house that reads surfaces. It read Wukong's face and saw a god; it reads Sanzang's and sees a gentleman; and in the passages to come it will read a piece of embroidered silk and see a life's purpose. The last line is a small marvel of unselfconscious syncretism: monks in a Chan cloister, having bowed to a Buddha and mistaken a monkey for a Daoist thunder-god, sit down in the strict Confucian order of precedence.