Sahih Muslim
The Book of Transactions (Kitab Al-Buyu)
Book Number: 010 / Hadith Number: 3667
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.