Sahih Muslim Book 10, Hadith Number 3667.

Chapter : Prohibition of the sale of fruits until they are clearly in good condition.

Ibn Umar (Allah be pleased with them) reported Allah’s Messenger (may peace be upon him) as saying: Do not buy fruit until its good condition becomes clear, and (the danger) of blight is no more. He said: Its good condition becoming clear implies that it becomes red or yellow.