It is narrated from Sayyiduna Zayd bin Thabit (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) came to Madinah while the people used to buy and sell fruit before it ripened. The Messenger of Allah (peace and blessings be upon him) heard a commotion and loud voices from the people and said: "What is this?" They said: O Messenger of Allah, these people had traded in the fruit of the date palms, and they now say that it was afterwards struck by blight. The Messenger of Allah (peace and blessings be upon him) said: "Then do not buy and sell it until it ripens."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4842