天高地厚 A Kindness High as Heaven
概眾小妖，俱盡燒死，卻將那老老爺解下救出，連孩兒都解救出來。此誠天高地厚之恩。不是他們，孩兒也死無疑了。如今山上太平，孩兒徹夜行走，也無事矣。」概众小妖，俱尽烧死，却将那老老爷解下救出，连孩儿都解救出来。此诚天高地厚之恩。不是他们，孩儿也死无疑了。如今山上太平，孩儿彻夜行走，也无事矣。」
逐句解 Line by line
every one of the little fiends together burned to death, and then they got that elder reverend gentleman untied and out, and got your child out and saved along with him.
俱盡燒死 — and 盡 here is raised to the exhausting reading by the tables rather than left at the sparing-and-limiting one it starts from, which is the same shift that governs the phrase for thanks-without-end twice in this chapter. 老老爺 stacks the respectful term twice over: the elder reverend gentleman.
This is truly a kindness high as heaven and thick as earth.
天高地厚 is the standard measure for a debt too large to state — the height of the sky and the depth of the ground. Eight characters, and they are the formal acknowledgement the whole visit exists to make.
If it were not for them, your child would have died without a doubt.
死無疑 is death beyond question. The woodcutter has now said three times in three different ways that he was going to die, which is what somebody does when they are still working out that they did not.
Now there is peace on the mountain, and your child can walk about all night long and come to no harm."
徹夜行走, to go about the whole night through, and 行 is the ordinary xíng. This is what the burning of the cave actually bought, stated by the only person qualified to say so: a man who cuts wood on that hillside can now do it after dark.
The last sentence is the chapter's real verdict on the fire, and it is not delivered by Wukong or by the narrator. It comes from a woodcutter explaining to his mother that the hill is safe now.
The novel has spent a page on a hundred creatures burning and given it two characters of pity. It now spends four characters on what that bought, and puts them in the mouth of somebody with everything to gain by it. It does not tell the reader how to weigh the two.