It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) forbade selling dates that are still on the trees in exchange for harvested dates by measure.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 15084
Hadith Gradingحکم دارالسلام:حديث صحيح، وهو مكرر: 15082