Yahya related to me from Malik from Abu'r-Rijal Muhammad ibn Abd ar-Rahman ibn Haritha from his mother, Amra bint Abd ar-Rahman that the Messenger of Allah, may Allah bless him and grant him peace, forbade selling fruit until it was clear of blight. Malik said, "Selling fruit before it has begun to ripen is an uncertain transaction (gharar) ."

Muwatta Malik Book 31, Hadith 12