Zhang Jian could not trust anyone else with the job since the other person might not even have been able to distinguish an edible fruit from a poisonous one given their meager knowledge of cultivation. As such he had set his mind to go look for the fruits in the woods near Mount Dabie as a start of his search.
He wanted to make one last effort before giving up on the goals that he had set for Wang Yan. He didn't want to give up before making that one last push.
Zhang Jian called Wu Ming and Wang Yan and told them about his plan. Of course he didn't mention to Wang Yan about his plan to fatten her up otherwise she might have impulsively hit him for his intentions to fatten up a girl especially a beautiful one like her who took great pride in her good looks.
After informing them of his approaching absence from the hut, Zhang Jian took the bamboo bucket from Wu Ming who reluctantly passed it on to him.