打誑語 Monks Telling Lies
三藏聞言道：「這猴兒，凡事便要自專。倘或那妖精神通廣大，你拿他不住，可不是我出家人打誑語麼？」行者笑道：「師父莫怪，等我再問了看。」三藏闻言道：「这猴儿，凡事便要自专。倘或那妖精神通广大，你拿他不住，可不是我出家人打诳语么？」行者笑道：「师父莫怪，等我再问了看。」
逐句解 Line by line
Hearing this, Tripitaka said, "This monkey. He must decide everything for himself.
自專 is to take a decision into your own hands without consulting anyone. The complaint is about procedure, not about the demon.
"If that demon's powers should turn out to be great and you cannot hold him, will that not make liars of us who have left the household life?"
打誑語 is monastic vocabulary: false speech is one of the cardinal prohibitions a monk takes on at ordination. Tripitaka's worry is a broken precept rather than a broken promise, which is a heavier thing.
Pilgrim laughed and said, "Do not be vexed, Master. Let me ask a little further and see."
問了看 — "ask, and then see" — puts off the commitment without withdrawing it.
Tripitaka has been silent for a long stretch and what rouses him is not the danger but the liability. He states it in the language of the precepts: if the boast fails, the failure is a moral one and it lands on all of them.
On the evidence so far the objection is also fair. Pilgrim has now made three claims about his own capability — the cudgel, the poem and the bow — and has been asked to make good on none of them.
The answer concedes nothing and buys time. He does not say he can catch the demon; he says he will ask more questions, which is what he does for the rest of the scene.