Sayyiduna Anas bin Malik (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) forbade selling the fruit of date palms before it ripens. We said to Sayyiduna Anas (may Allah be pleased with him): What is its ripening? He said that it turns red. He (peace and blessings be upon him) said: "When Allah withholds the fruit, then how will your brother's wealth be lawful for you?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10595