人喊馬嘶 Men Shouting Horses Neighing
闖入深山，依著舊路。正走處，忽聽得人喊馬嘶之聲。即舉目觀之，原來是獅駝洞口有萬數小妖排列著槍刀劍戟，旗幟旌旄。闯入深山，依着旧路。正走处，忽听得人喊马嘶之声。即举目观之，原来是狮驼洞口有万数小妖排列着枪刀剑戟，旗帜旌旄。
逐句解 Line by line
He plunged into the deep mountain, keeping to the old road.
依著 with 著 as zhe — following along, the road held to throughout. 闖 is to burst in, a horse forcing a gate.
As he was going along, he suddenly heard the sound of men shouting and horses neighing.
人喊馬嘶 is a set four-character phrase for an army in the field. 聽得 keeps 得 as dé, the perception suffix.
Lifting his eyes to look, he found that at the mouth of the Lion Camel Cave there were tens of thousands of little demons drawn up with spears and swords, blades and halberds, banners and standards and pennons.
萬數 is tens of thousands. 排列著 has 著 as zhe again, the formation standing. Then two four-character lists — 槍刀劍戟 and 旗幟旌旄 — which is how this novel writes an army: not a number but an inventory of edges and cloth.
The forty-eight thousand stop being a figure in a report and become a sound. Men shouting, horses neighing, heard before anything is seen.
Then the sight, given as two lists of four. Spears, swords, blades, halberds; banners, standards, pennons — weapons first and then colours, which is the order you would see them in as you came round a hill.
Everything the chapter has spent four thousand characters arguing about is now standing in front of one monkey in a dead demon's uniform.