Musnad Ahmad 938:6

Muhammad ibn Mus'ab narrated to us, al-Awza'i narrated to us, from al-Zuhri, from Salim, 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 (the sale of fresh dates on the tree for dried dates), that they may be sold by their estimation, and he did not grant a concession in anything other than that."