Sayyidina Ibn Umar (RA) reported that Allah’s Messenger forbade sale of dates till they were brilliant in colour.
[Ahmed 4493, Muslim 1535, Abu Dawud 3368, Nisai 4565]
With the same sanad, it is reported that the Prophet (SAW) forbade sale of wheat till they were white and safe from calamity. He forbade (both) the buyer and the seller.