Mukhtasar Muslim

It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Noble Prophet (peace and blessings be upon him) forbade selling dates until they become red or yellow (because when redness or yellowness appears in them, safety is assured), and likewise, he forbade selling ears (of grain) until they become white and are safe from calamity. He forbade the seller from selling and the buyer from buying.