寸草不生 Not A Blade Grows There
三藏道：「火焰山卻在那邊？可阻西去之路？」老者道：「西方卻去不得。那山離此有六十里遠，正是西方必由之路，卻有八百里火焰，四週圍寸草不生。若過得山，就是銅腦蓋，鐵身軀，也要化成汁哩。」三藏聞言，大驚失色，不敢再問。三藏道：「火焰山却在那边？可阻西去之路？」老者道：「西方却去不得。那山离此有六十里远，正是西方必由之路，却有八百里火焰，四周围寸草不生。若过得山，就是铜脑盖，铁身躯，也要化成汁哩。」三藏闻言，大惊失色，不敢再问。
逐句解 Line by line
Tripitaka said, 'And whereabouts is this Mountain of Flames? Does it block the road westward?'
那邊 asks rather than points here — nǎ, "whereabouts" — not the nà of "over there." Tripitaka puts the two questions that matter to him in the right order: where is it, and is it in my way.
The old man said, 'Westward there is no getting through at all.'
去不得 means "cannot get through": 得 is the light toneless de of what is possible, not the dé of 只得 a moment ago. Two readings of one character, nine characters apart.
'That mountain lies sixty lǐ from here, and it is precisely the road one must take going west; but there are eight hundred lǐ of flame upon it, and for its whole circuit not a blade of grass grows.'
A lǐ in this period runs to roughly half a kilometre; house practice is to leave the unit in Chinese rather than swap in a Western one. 必由之路, "the road one must go by," is a set phrase. That figure of eight hundred lǐ of fire is the obstacle the next three chapters exist to clear.
'If one tried to get across that mountain, then though one had a skull of bronze and a body of iron, one would still be melted down to liquid.'
過得山 again turns on whether a thing is possible, so 得 is de. 銅腦蓋，鐵身軀 — a bronze skull and an iron body — is everyday hyperbole for being indestructible. 哩 closes the sentence as the weightless li, which is precisely the reading the place name 斯哈哩 had to be kept away from.
Hearing this, Tripitaka went pale with alarm and did not dare ask any further.
大驚失色, startled badly enough to lose the colour in your face. Tripitaka's answer to an obstacle is always to stop asking — and the narrative is about to hand the problem to Pilgrim, who is currently outside buying cake.
Tripitaka asks the two questions any traveller asks — where is it, is it in the way — and gets an answer that shuts the road. Sixty lǐ to the mountain, eight hundred lǐ of fire across it, and the flat statement that this is precisely the route west. No alternative is offered because the geography does not allow one.
The old man's hyperbole is well judged. A bronze skull and an iron body would melt to liquid: the image concedes in advance every objection about toughness or magic a listener might raise, which happens to be exactly the objection this particular party is entitled to raise. It is also, as the chapter will show, not quite true — Pilgrim will cross the fire and lose nothing but the hair on his legs.
Tripitaka goes pale and stops asking, and the narrative lets him. He has been handed an obstacle with no solution in any terms he understands, and his job at such moments is to register despair while somebody else finds the way through. That somebody is at this moment out in the road buying a cake off a man with a red cart, for reasons that will turn out to matter a great deal.