口出大言 Big Words And Deep Measure
太監聞言，無不驚駭。校尉道：「口出大言，必有度量。我等著一半在此啞請，著一半入朝啟奏。」太监闻言，无不惊骇。校尉道：「口出大言，必有度量。我等着一半在此哑请，着一半入朝启奏。」
逐句解 Line by line
The eunuchs heard it and were struck with alarm to a man.
無不 is the double negative of formal storytelling: not one of them was unafraid. It is a stiffer way of saying they were all terrified, and the stiffness is the point in a room full of officials.
A guardsman said, "A man whose mouth utters big words must have depth to match.
量 reads liàng in 度量, capacity or generosity of mind. The other reading liáng belongs to measuring things out, and it has no place in a line of prose dialogue.
"Let half of us stay here and make our silent request, and half go into court and report."
著 is zhuó at both sites — setting somebody to a task, the same construction as 著你遠涉山川 in the rhapsody and 著沙僧安排茶飯 at the hostel, and not the weak zhe. 啞請 is to petition without speaking, by staying on one's knees.
口出大言 could be read as scepticism and is not. The guardsman takes the boast as evidence — a man who talks that large must be able to back it — which is exactly the inference Pilgrim was fishing for.
啞請 is a marvellous detail. Half the delegation will simply stay on its knees in the hostel and say nothing, as a form of pressure, while the other half goes to fetch the king. Nobody has asked them to do either.