千百口剃頭 A Thousand Razors
又將金箍棒取在手中，掂一掂，幌一幌，叫聲：「寶貝，變！」即變做千百口剃頭刀兒。他拿一把，吩咐小行者各拿一把，都去皇宮內院、五府六部、各衙門裡剃頭。又将金箍棒取在手中，掂一掂，幌一幌，叫声：「宝贝，变！」即变做千百口剃头刀儿。他拿一把，吩咐小行者各拿一把，都去皇宫内院、五府六部、各衙门里剃头。
逐句解 Line by line
Then he took the gold-banded staff in his hand, weighed it, gave it a shake and called: "Treasure — change!"
掂一掂 is to test the weight of a thing in the hand, and 幌一幌 to give it a shake — both verbs doubled around a 一, the spoken pattern that makes an action brief and casual.
It became a thousand and more head-shaving razors.
千百口 is a thousand or a hundred, meaning a great many; 口 is the measure word for blades. The staff weighs thirteen thousand five hundred catties and holds up the Milky Way in the old story. It is now a crate of barber's razors.
He took one himself, told each little Pilgrim to take one, and off they all went into the palace and the inner courts, the six ministries and the five offices and every department, to shave heads.
The last two characters are the whole plan and the novel has not announced it until now. 剃頭 is simply to shave a head, the barber's ordinary word.
The reveal is held to the last two characters of the passage, and it is worth the wait. A reader braced for a massacre gets a haircut.
It is also the exact answer to the problem. The king kills monks, and a shaved head is what marks a monk out — a fact the pilgrims have spent the whole chapter hiding behind headcloths. Pilgrim hands that mark to everybody in the government and makes it worth nothing.