It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) forbade the sale of dates until they ripen, and the Prophet (peace and blessings be upon him) issued this prohibition for both the seller and the buyer.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5292
Hadith Gradingحکم دارالسلام:إسناده صحيح ، م : 1535 .