查勘你們 Checking For False Ones
行者道：「大王要吃唐僧，只怕孫行者神通廣大，說他會變化，只恐他變作小鑽風，來這裡屣著路徑，打探消息，把我陞作總鑽風，來查勘你們這一班可有假的？」行者道：「大王要吃唐僧，只怕孙行者神通广大，说他会变化，只恐他变作小钻风，来这里屣着路径，打探消息，把我升作总钻风，来查勘你们这一班可有假的？」
逐句解 Line by line
Pilgrim said, "The king means to eat the Tang Monk, but he is afraid of Sun the Pilgrim, whose powers are said to be vast; they say he can change his shape, and the king fears he may turn himself into a Little Borer of the Wind and come treading these paths here to spy out the news — so he has raised me to Chief Borer of the Wind, to come and inspect this shift of yours and find out whether there are any false ones among you."
Sixty-one characters in one breath, the third-longest unit in the chapter. 屣著路徑 has 著 as zháo, contact achieved — treading the paths, the same compound Bajie used of brushing the mountain's edge. 查勘 is to inspect and verify, and 假的 is the false ones. Pilgrim has described himself accurately, warned them against himself, and given himself authority to interrogate them for being him.
This is the best lie in the novel and it is made entirely of true statements. The king does mean to eat the Tang Monk. Sun the Pilgrim can change shape. He has turned into a Little Borer of the Wind. He is here spying out the news.
The only false element is the promotion, and the promotion is what licenses him to hunt for the impostor. He has built a warrant out of a confession.
It also explains the muttered warning the courier was chanting. Somebody on this mountain really did brief the patrols about a monkey who turns into flies, and Pilgrim has taken that briefing and made himself its enforcement officer.