Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) forbade "al-muzabanah" (muzabanah), and muzabanah is that "a person sells the fruit of his garden: if it is dates, they are sold for dry dates by a fixed measure; if it is grapes, he sells his grapes for raisins by a fixed measure; if it is a crop, he sells it for a fixed measure of grain." He (peace and blessings be upon him) forbade all of these.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10638