Yahya related to me from Malik from Abu'z-Zinad from Kharija ibnZayd ibn Thabit that Zayd ibn Thabit did not sell fruit until thePleiades were visible, at the end of May.Malik said, "Theway of doing things among us about selling melons, cucumbers, water-melons, and carrots is that it is halal to sell them when it is clearthat they have begun to ripen. Then the buyer has what grows until theseason is over. There is no specific timing laid down for that becausethe time is well known with people, and it may happen that the cropwill be affected by blight and put a premature end to the season. Ifblight strikes and a third or more of the crop is damaged, anallowance for that is deducted from the price of purchase."
USC-MSA web (English) reference: Book 31, Hadith 13
Arabic reference: Book 31, Hadith 1305