Sahih Bukhari, Chapter: Sales and Trade

In the lifetime of the Prophet (SAW), the people used to trade with fruits. When they cut their date-fruits and the purchasers came to recieve their rights, the sellers would say, 'My dates hace got rotten; they are blighted with disease, they are afflicted with Qusham (a disease which causes the fruit to fall before ripening).' They would go on complaining of defects in their purchases. Allah's Messenger (SAW) said, "Do not sell the fruits before their benefit is evident (i.e., free from all the dangers of being spoiled or blighted), by way of advice for they quarrelled too much." Kharija bin Zaid bin Thabit said that Zaid bin Thabit used not to sell the fruits of his lands till Pleiades appeared and the one could distinguish the yellow fruits from the red (ripe) ones.