A man from the people of Najran asked Sayyiduna Ibn Umar (may Allah be pleased with them both) about making a salam sale in dates. He said: A man made a salam sale in dates with another man, and that year the palms bore no fruit. He put the matter before the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Why do you consume his wealth?" He (peace and blessings be upon him) ordered him to return (the price) to him for the sale. Then he (peace and blessings be upon him) forbade making a salam sale in dates until the fruit ripens.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11112