關了南天門 They Shut The Southern Gate
諕得眾天兵不敢交鋒，關了南天門。故此是一口曾吞十萬兵。」行者聞言，暗笑道：「若是講手頭之話，老孫也曾幹過。」諕得众天兵不敢交锋，关了南天门。故此是一口曾吞十万兵。」行者闻言，暗笑道：「若是讲手头之话，老孙也曾干过。」
逐句解 Line by line
It so frightened the heavenly host that they dared not join battle, and shut the Southern Gate of Heaven.
諕得 is the fright-and-consequence construction, with 諕 as xià and 得 unstressed. 南天門 is the main gate of the celestial city, and shutting it is heaven conceding a siege.
That is how he came to swallow a hundred thousand troops at one gulp."
Ten characters closing the account, and they simply restate the claim Pilgrim called a lie. The demon has proved his point by telling the story behind it.
Hearing this, Pilgrim laughed to himself. "If we are talking about handiwork of that sort, Old Sun has done it too."
手頭之話 is talk about what one's hands have done — a matter of track record. And 也曾幹過 is the admission the whole passage has been waiting for: I have done that as well.
Heaven shutting its own front gate is the detail that sells the story. Not a defeat in the field but a decision to stop coming out, which is a far more humiliating thing to record.
Pilgrim's private laugh is the chapter's quietest and best moment. He does not dispute the story any further. He observes that he has done the same, and he is right — the parallel has been exact for two passages.
It changes what the interrogation is. He is no longer measuring an enemy against nothing; he is measuring one against himself, and so far the scores are level.