Musannaf Ibn Abi Shayba 35:153

Ali bin Hashim narrated to us, from Ibn Abi Layla, from Atiyyah, from Abu Sa’id, who said: The Prophet (peace and blessings of Allah be upon him) forbade the selling of fruit until its soundness becomes apparent. They said: "And what is the appearance of its soundness?" He said: "Its blights depart and its sweetness becomes pure."