腹中空虛 My Belly Is Empty
叫：「八戒，跟我去來。」八戒道：「謹依兄命。但只是腹中空虛，不好著力。」叫：「八戒，跟我去来。」八戒道：「谨依兄命。但只是腹中空虚，不好着力。」
逐句解 Line by line
He called out, "Bajie, come along with me."
Seven characters, no explanation. Wukong gives orders to his fellow disciples the way he gives them to local gods.
Bajie said, "I respectfully obey my brother's command.
The formality is a joke and everyone in the scene knows it. 謹依兄命 is the language of a junior officer accepting orders, and Bajie is about to spoil it completely in the very next breath.
Only my belly is empty, and I shall not be much good at putting out strength."
著力 takes zhuó — applying force, putting your back into it — one of the lexical uses of the character rather than a grammatical one. The complaint is Bajie's signature move and it is never merely comic: he is the only member of the party who consistently says out loud that bodies need feeding.
The two-beat structure is the whole joke. Formal acceptance, then the condition. Bajie does this so reliably that the novel can set it up in fourteen characters and trust the reader to see it coming.
It is also a small piece of characterisation for Wukong, who never eats and never understands why anyone else needs to. The party's two extremes — the ape who lives on air and the pig who cannot fight on an empty stomach — are set side by side here without a word of comment.