帶挈帶挈 Do Not Play Tricks On Me
八戒道：「也罷，也罷，望你帶挈帶挈。但只急溜處，莫捉弄我。」長老道：「八戒在意，我與沙僧在此。」八戒道：「也罢，也罢，望你带挈带挈。但只急溜处，莫捉弄我。」长老道：「八戒在意，我与沙僧在此。」
逐句解 Line by line
Bajie said, "All right, all right. I'll look to you to carry me along."
也罷 doubled is the sound of giving in, and the sealed chapters read it yě bà at all eight of their sites. 帶挈 is to bring somebody along and let them share in the benefit — a favour word, and doubling it makes it a wheedle.
"Only when things get fast and slippery, don't play tricks on me."
急溜處 — the quick and slippery moments — is the same 溜 the third chief used about Wukong being too slippery to hold. And the request is the whole history of these two in eight characters: Bajie's fear is not the demons, it is his brother.
The elder said, "Bajie, take care. Sha Monk and I will be here."
在意, keep your mind on it, take care. Xuanzang addresses the frightened one by name and tells him where the rest of them will be, which is the correct thing to say and the only comfort available.
Bajie's condition for going is not about the demons at all. He has spent seventy chapters being tricked, blamed and left holding things by the brother he is now agreeing to follow into a cave, and the one term he negotiates is that it should not happen again. It will happen again.
Xuanzang's line closes the scene with unusual tact. He does not tell Bajie to be brave or promise that it will be fine. He tells him that the two of them will be right here — which is a smaller and more honest thing to offer, and it is what sends the Idiot up the mountain.