It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) forbade selling fruit on the tree before it ripens. He (peace be upon him) was asked, "What do you mean by 'tazhu'?" He (peace be upon him) replied: "Until it becomes red." Then the Messenger of Allah (peace and blessings be upon him) said: "What do you think, if a calamity befalls the fruit, then for what will he take money from his Muslim brother?"
Hadith Referenceالسنن المأثورة / باب في البيوع / 192
Hadith Takhrijصحیح بخاری، الزكاة، باب من باع ثماره أو نخله ...... الخ، رقم : 1488 ، صحیح مسلم ، المساقاة، باب وضع الحوائج ، رقم : 1555 ۔