Nafi' narrates from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) "forbade selling fruit before it ripens"; he (peace and blessings be upon him) "forbade both the seller and the buyer."
(b) In the narration of Imam al-Shafi'i (may Allah have mercy on him) the words are "the sale of fruits", and mushtari (buyer) in place of mubta' (buyer).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10587