馬快如飛 The Horse Quick As Flight
那獃子趕著沙僧，廝耍廝鬥。老師父馬快如飛。須臾，到那山崖之邊，一步步往上行來。那呆子赶着沙僧，厮耍厮斗。老师父马快如飞。须臾，到那山崖之边，一步步往上行来。
逐句解 Line by line
The idiot went chasing after Sha Monk, the two of them larking and scuffling as they walked.
Two of them are messing about as they walk. Doubling 廝 in front of a pair of verbs is the vernacular way of saying each at the other, and setting 耍 beside 鬥 turns the fight into a game. 著 is the aspect particle zhe on 趕, not the zhuó of wearing something.
The old master's horse went quick as flight.
Seven graphs of narrator on their own. The horse is a dragon prince under a borrowed shape, and the novel has a habit of mentioning how fast it goes at exactly the moments when the party is about to arrive somewhere it should not.
In a moment they had reached the foot of the cliff and were working their way up it step by step.
The ground turns upward and the pace turns careful: 一步步, step by step. 行 is xíng here. It is the first of several places in this chapter where the automatic reading offers háng, the reading for a written line or a trade, and nothing in the text calls for it — all fifty-six occurrences are xíng.
Thirty-three graphs to move the party from level ground to the foot of a cliff, and the pace of the prose matches the pace of the walk: two disciples scuffling, a horse going fast, and then 一步步 as the ground tilts.
The arrangement is a small piece of characterisation done without comment. Eight Rules and Sha Monk are horsing about at the back, Tripitaka is out in front on an animal he is not controlling, and Pilgrim is not mentioned at all until the beasts turn up.