Pilgrim said, "You call him a horse, but he is no common horse. He was in truth the son of Ao Run, Dragon King of the Western Sea, and went by the name Dragon-Horse, the Third Prince."

Wukong shuts the argument down by telling Bajie what the horse actually is. This white steed is the dragon-prince of chapter fifteen: 龍馬三太子, the Third Prince, Dragon-Horse. 敖閏 (Ào Rùn) is Dragon King of the Western Sea in the 世德堂本, the edition this site follows; some other editions read 敖順 instead. Both 之子, son of, and 三太子, Third Prince, take 子 as the full noun zǐ rather than the unstressed suffix.

"Only because he set fire to the hall and burned the luminous pearl there, his own father charged him with unfilial revolt; having broken the statutes of Heaven, he owed his very life to the mercy of the Bodhisattva Guanyin, who delivered him."

The prince's crime, in one breath. 明珠 is the night-shining pearl he burned; 忤逆 (wǔ nì) is the capital charge of revolt against a parent, and it was his own father who laid it; 天條 is the statute book of Heaven. The three 了 here — 燒了, 告了, 救了 — are all the little completed-action le.

"There at the Eagle's-Sorrow Steep-Gorge he waited long for the Master; and by good fortune the Bodhisattva came in person, stripped him of his scales, drew off his horns, plucked the pearl from beneath his throat, and only then made him into this horse — willing to bear the Master westward to worship the Buddha."

鷹愁陡澗 (Yīngchóu Dǒujiàn), the Eagle's-Sorrow Ravine, again from chapter fifteen. 幸得 takes the full verb dé, obtained, was granted — worth holding on to, because Bajie is about to use the same character as the light de a few lines down. 將 is the handling-word jiāng: took him and stripped his scales. 退鱗去角 is the un-dragoning itself, scales off, horns drawn, pearl plucked from the throat — a prince dismantled into a pack animal.

"All this is each one's own store of merit — do not measure yourself against him."

功果 (gōng guǒ), merit-fruit, is the karmic account each pilgrim is running toward buddhahood. 攀 is pān, to drag someone in by comparison, to measure yourself against them. 都 reads dōu, all of it. The rebuke is doctrinal and also just brotherly: mind your own ledger.

Sha Monk, hearing this, said, "Elder brother — is he truly a dragon?"

真個 (zhēn gè) is the colloquial really, truly; 麼 is the question particle on the end. Sha Monk has been travelling with this horse for a chapter and is only now finding out.

"A dragon," said Pilgrim.

Two words. The storyteller's beat, held just long enough for Bajie to fill it with a lecture.

Bajie said, "Brother, I have heard the ancients say: a dragon can spew cloud and belch fog, scatter earth and fling up sand; it has the craft to cleave hills and split ridges, the power to overturn rivers and churn seas."

Bajie has read something about dragons and is not going to waste it. The list is stock dragon-lore — spew cloud, belch fog, scatter earth, fling sand, overturn rivers, churn seas. 聞得 takes the light de, have heard, and it is the exact mirror of 幸得 with its full dé three lines above; the same character, two weights. 巴山㨝嶺, to cleave hills and split ridges, contains 㨝 (xiē), a rare hand-radical verb of wedging or splitting — the only character of its kind in the whole chapter. 噯 (ài) is to belch forth.

"How is it that today he plods along at such a crawl?"

這等 (zhè děng) is in this manner, like this; 慢慢而走 is an unhurried amble. The whole learned digression exists to set up this one deflating question.

Pilgrim said, "You want him to go fast? I'll make him go fast for you to see."

教 is jiào, the causative make or cause. 個兒 is a colloquial tail on the verb — 快走個兒, put on a bit of speed. Wukong is about to be helpful in the worst possible way.