卻都心良 Ugly of Face but Good of Heart
那王子舉目見那等醜惡，卻也心中害怕。三藏合掌道：「千歲放心。頑徒雖是貌醜，卻都心良。」那王子举目见那等丑恶，却也心中害怕。三藏合掌道：「千岁放心。顽徒虽是貌丑，却都心良。」
逐句解 Line by line
The prince raised his eyes, saw how hideous they were, and was frightened in his heart after all.
卻也 is a small concessive — after all, in spite of everything. It concedes on the prince's behalf what he would rather not admit: he is a worthy and open-minded ruler who has just been handed a fright he cannot govern away. The novel is fond of this moment, where a good man's composure fails him for entirely reasonable reasons.
Tripitaka pressed his palms together and said, "Set your mind at rest, Your Highness.
千歲 again, a thousand years, the acclamation for a prince — the second of the three times it occurs in this chapter, against not one instance of the ten-thousand-year form reserved for emperors. Tripitaka has been consistent about the man's rank from the moment he walked in.
My unruly disciples are ugly of face, but their hearts are all good."
頑徒, unruly disciple, is Tripitaka's standing self-deprecation about his own household — you belittle your own people the way you belittle your own house. The sentence is built as a concession followed by a correction, ugly but good, and this exact formula is about to come back twice more in the chapter, once from Sha Monk and once in a way that finally convinces somebody.
The prince has been generous, competent and welcoming for two full scenes, and then three faces walk into the room and he is simply afraid. The novel does not hold it against him.
Tripitaka's defence is the sentence he has been making in one form or another since the start of the pilgrimage: they look terrible and they are good. He will not be believed today.
It is worth noticing that this is the whole moral machinery of the chapter, stated early and plainly. Everything from here to the weapons in the courtyard argues one question: whether a face tells you what a creature is.