做孫子 Your Rake Could Be Its Grandson
二王子掣開步，雙手舞鈀，便要打八戒。八戒嘻嘻笑道：「你那鈀只好與我這鈀做孫子罷了。」二王子掣开步，双手舞钯，便要打八戒。八戒嘻嘻笑道：「你那钯只好与我这钯做孙子罢了。」
逐句解 Line by line
The second prince stepped out, swung his rake in both hands, and made to strike Bajie.
掣開步 is to draw the feet apart into a fighting stance — the boy sets himself properly before he swings, which tells you he has been taught. He has also chosen, out of everyone in the room, the one opponent whose own weapon is a rake.
Bajie grinned and said, "That rake of yours is fit to be a grandson to this rake of mine."
The insult is a very Chinese shape: you belittle a thing by assigning it a junior place in a family. 做孫子, to be a grandson, puts the prince's rake two generations below Bajie's. 罷了 at the end is the dismissive tag — and that is all it is fit for. 嘻嘻 is the sound of a wide, unbothered grin, which is exactly the wrong response to a weapon coming at your head.
Of the three princes it is the second who moves first, and he moves at Bajie, whose rake he has unknowingly been imitating for years.
Bajie's reply is the perfect measure of how little danger he is in. He does not block, dodge or draw. He makes a joke about the boy's family tree and lets the rake come.