輕那慢步 He Moved Lightly And Slowly
約有三更時分，孫大聖輕那慢步，走入裡面，原來一層層門戶甚緊。他就爬上高樓看時，窗牖皆關。欲要下去，又恐怕窗櫺兒響，不敢推動。捻著訣，搖身一變，變做一個仙鼠，俗名蝙蝠。约有三更时分，孙大圣轻那慢步，走入里面，原来一层层门户甚紧。他就爬上高楼看时，窗牖皆关。欲要下去，又恐怕窗櫺儿响，不敢推动。捻着诀，摇身一变，变做一个仙鼠，俗名蝙蝠。
逐句解 Line by line
It was about the third watch. Sun the Great Sage shifted his weight lightly and stepped slowly, went in, and found the doors shut fast layer upon layer.
那 reads nuó here, standing in for 挪, to shift your weight — the same borrowing the novel uses in 騰那 — and it is the only one of the graph's five occurrences in this stretch that is not the ordinary demonstrative. 更 is gēng, the night watch again.
He climbed the high tower and looked, and every window and casement was shut.
窗牖 puts the two words for a window side by side, one everyday and one literary, which is how the sentence says all of them without counting any.
He meant to go down, and then was afraid the window lattice would creak, so he did not dare push at it.
The most careful the Great Sage has been all chapter, and it is over a lattice that might creak. 兒 on 窗櫺 is the throwaway suffix with the neutral tone, as it is at every prose occurrence in the chapter — five segments on the same graph will carry a full syllable, because a poem needs it for a rhyme.
He made a sign, shook himself, and changed into an immortal rat — the common name is a bat.
The joke is that a Great Sage in the middle of transforming himself insists on the elegant name first — an immortal rat — and the narrator has to translate: 俗名蝙蝠, the common name is a bat. Four graphs, mid-sentence.
Everything in this passage is about being quiet. He shifts rather than walks, steps slowly, climbs instead of opening, and then declines to push a window in case the lattice creaks. It is the most careful the Great Sage has been in the chapter, and it is for a bundle of clothes.
The transformation is chosen for the same reason. A bat gets through a gap without opening anything — and the poem that follows spends all four of its couplets on what a bat is good at rather than on what this one is doing.