沉魚落雁 Fish Sink and Geese Fall
那怪見他來問，淚如泉湧。你看他桃腮垂淚，有沉魚落雁之容；星眼含悲，有閉月羞花之貌。那怪见他来问，泪如泉涌。你看他桃腮垂泪，有沉鱼落雁之容；星眼含悲，有闭月羞花之貌。
逐句解 Line by line
When the fiend saw him come and ask, her tears welled like a spring.
淚如泉湧 — tears welling like a spring — is the first of three separate accounts of her weeping in this one scene. The book is counting them for us.
Look at her: tears down peach-blossom cheeks, with a face to make the fish sink and the wild geese drop;
沉魚落雁 is the oldest compliment in the language and its origin is a joke. Zhuangzi wrote that when the famous beauties appeared, fish dived deep and birds flew high — his point being that fish and birds have no interest whatever in human beauty and simply fled. Later ages took the phrase as praise and have used it that way ever since.
starry eyes brimming with grief, with a look to shut the moon away and shame the flowers.
閉月羞花 is the matching half — the moon hides itself and the flowers are embarrassed. Chinese pairs the two phrases so habitually that quoting one calls up the other, and this couplet uses both in eleven characters.
The book is laying it on with a trowel and the excess is deliberate. Two of the most worn beauty phrases in the language, back to back, applied to something the narrator has just told us is a demon.
The tears come first, before either compliment, and that is the real machinery. She is not simply beautiful. She is beautiful and crying, which is a combination engineered to shut down exactly the faculty Tripitaka needs. Every phrase in this passage is borrowed, and the borrowing is the tell: she is not being described, she is being assembled out of stock parts.