陰風刮動 When You See The Shade Wind
可速為之，略遲緩些，恐無及也。」行者抖擻神威，即起身，吩咐八戒、沙僧：「同師父坐著，等我施為，你看但有陰風刮動，就是小兒出城了。」他三人一齊俱念：「南無救生藥師佛！南無救生藥師佛！」可速为之，略迟缓些，恐无及也。」行者抖擞神威，即起身，吩咐八戒、沙僧：「同师父坐着，等我施为，你看但有阴风刮动，就是小儿出城了。」他三人一齐俱念：「南无救生药师佛！南无救生药师佛！」
逐句解 Line by line
"Set about it quickly — if you delay even a little, I fear it will be too late."
為 is wéi, to do — do it quickly. The urgency is real: the operation is scheduled for noon tomorrow, which nobody in the room has said aloud but everybody has worked out.
Pilgrim roused his divine power, rose at once, and gave his orders to Bajie and Sha Monk: "Sit here with the master, and let me get to work. When you see a shade-wind blowing, that will be the children leaving the city."
著 is zhe, the running marker — sit here and stay sitting. 施為 takes 為 as wéi: to set to work, to act. 陰風 yīn fēng is the cold wind that accompanies spirits, and Wukong is telling them not to be alarmed by it — which is also the novel telling the reader what the next block will look like.
The three of them chanted together, "Namo Medicine Master Buddha who saves life! Namo Medicine Master Buddha who saves life!"
南無 is ná mó, not the everyday reading of those two characters — it transcribes the Sanskrit namo, an act of homage, and it opens Buddhist invocations the way "hail" does in English. The Medicine Master, Bhaiṣajyaguru, is the healing Buddha, and the three of them have picked exactly the right one: the children are about to be carried off to keep a sick man alive, and the Buddha they call on is the one whose vows are about curing illness without harm.
The chapter's action finally begins, and it begins with three people sitting still and saying the same six characters over and over. The novel gives Wukong one sentence of instruction and then leaves him; what it shows is the ones who have to wait.
The choice of Buddha is not decoration. The whole crisis is a medical one — a dying king, exhausted physicians, a prescription that requires killing — and the invocation the party reaches for is to the healing Buddha, whose great vows include curing the sick and relieving those under sentence of unjust punishment. The chapter has put the right deity in the room, and has done it without a word of explanation.