Musnad Ahmad 27:787

Waki’ narrated to us, from Isra’il, from Abu Ishaq, from al-Najrani, from Ibn ‘Umar, that two men traded palm trees during the time of the Prophet, may Allah bless him and grant him peace, before the fruit had appeared, and it did not produce anything. The Prophet, may Allah bless him and grant him peace, said: "Upon what basis do you consume his wealth?" And he forbade the sale of fruit until its soundness becomes apparent.