It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) forbade the sale of grain that had not been measured. The narrator Sufyan (may Allah have mercy on him) says that by measuring, what is meant is taking possession. Tawus (may Allah have mercy on him) says that this was the opinion of Ibn Abbas (may Allah be pleased with him); in my view, this ruling applies to all things. (That is, whether it is grain or anything else, nothing should be sold to another before taking possession.)
Hadith Referenceالسنن المأثورة / باب في البيوع / 226
Hadith Takhrijصحیح بخاری، البيوع، باب بيع الطعام قبل ان يقبض وبيع ما ليس عندك، رقم: 2135، صحیح مسلم، البيوع، باب بطلان بيع المبيع قبل القبض، رقم: 1525