Musnad Ahmad 938:63

Muhammad ibn Ubayd narrated to us, Ubayd Allah narrated to us, from Nafi, from Ibn Umar, from Zayd ibn Thabit: "That the Messenger of Allah (peace and blessings of Allah be upon him) granted a concession regarding the sale of 'Araya (dates on the palm tree) for their estimated value in dried dates, by measure."