渺然不見 Gone in a Single Sound
行者聞言，即吩咐沙僧、八戒保護師父，又教土地陪伴勿回。隨即忽的一聲，渺然不見。那裡消半個時辰，早見一座高山凌漢。行者闻言，即吩咐沙僧、八戒保护师父，又教土地陪伴勿回。随即忽的一声，渺然不见。那里消半个时辰，早见一座高山凌汉。
逐句解 Line by line
Pilgrim, hearing this, at once gave orders that Sha Monk and Eight Rules should guard the Master, and charged the Local Spirit to keep them company and not withdraw.
教 is jiào, to order somebody to do something, not jiāo, to teach. And 勿回 is an instruction rather than a forecast: the Local Spirit is not to slip away the moment the Sage's back is turned.
Then with a sudden sound he was away, and vanished into nothing.
忽的一聲 is a stock vernacular formula where a noise stands in for the movement itself — there is a sudden sound, and that is the departure. 一 shifts to yì before the level tone of 聲.
Scarcely had half a watch been spent when he saw before him a high mountain piercing the sky.
那裡 here is a colloquial spelling of the question-word pair, and means "hardly" or "scarcely" rather than "where" — so 那 is nǎ, not the pointing nà. 消 is to use up, of time. And 凌漢 is to ride over the Cloudy Han, which is what Chinese calls the Milky Way — a river of stars rather than a spill of milk.
Three sentences carry the Great Sage three thousand 里. The economy is characteristic: the orders take one clause, the departure takes a sound, and the arrival is measured not in distance covered but in how little time it used up. Where the Local Spirit's speech laboured over reasons and consequences, the Sage simply goes.
The instruction to the Local Spirit is worth a second look. He is not dismissed; he is detained — told to stay with the others and not withdraw. The Great Sage has just been informed by this deity that the fire is his own doing and that the deity's freedom depends on his success. Keeping him beside the Master is half courtesy and half collateral.