Musnad Ahmad 938:9

Sufyan narrated to us, from al-Zuhri, from Salim, from his father, that the Prophet, peace and blessings of Allah be upon him, "forbade the selling of fruit for dates." Then Zayd ibn Thabit informed them: "That the Messenger of Allah, peace and blessings of Allah be upon him, granted a concession regarding the *'araya* (the sale of fresh dates on the tree for dried dates of equivalent measure)."