Wei Wuxian hides his face against the other man when the donkey kicks at the half door with a front leg. Clearly he wants out even if he can't make any promises to not kick the person doing it.

The boy slowly turns to peek at the donkey again though as he waits for big brother to open the stall. He points his finger at the donkey, "Be good."

The donkey just gives another impatient kick to the door in response.