恐滅苗裔 A Show of Reluctance
那道士吹打已畢，行者開言道：「那晚輩小仙，不須拜伏。我欲不留些聖水與你們，恐滅了苗裔；若要與你，又忒容易了。」那道士吹打已毕，行者开言道：「那晚辈小仙，不须拜伏。我欲不留些圣水与你们，恐灭了苗裔；若要与你，又忒容易了。」
逐句解 Line by line
When the Daoists had finished their piping and drumming, Pilgrim spoke up: “You juniors of the immortal ranks, you need not prostrate yourselves.
那道士 and 那晚輩: 那 = nà both times, pointing at people who are there. 吹打 "piping and drumming," the ritual band. 不須: 不 = bù.
I was of a mind not to leave you any holy water, fearing it might cut off your line;
我欲 "I was inclined to." 不留: the rising tone of 留 keeps 不 at bù. 苗裔 "offspring, posterity, a line of descent" -- Wukong is gravely warning them that the gift might sterilise them, which is the sort of detail a real god would never think to invent.
but were I to give it you, it would come too easily.”
忒容易: 忒 (tè) "too, excessively." The whole show of hesitation is Wukong stretching the joke out because he can.
Wukong plays the reluctant donor: first a solemn reason to withhold the gift, then a solemn reason to grant it. It is pure delay, and it works on the audience the way it works on the Daoists, by making them want the thing more.
"It would come too easily" is a small parody of how scarcity makes a favour precious. He is inventing divine reluctance from first principles and getting it about right. The audience, of course, knows what the boon actually is, and every pious word in the passage is sharpened by that knowledge.