Musannaf Ibn Abi Shayba 13:3125

Abu Bakr narrated to us, he said: Hafs narrated to us, he said: I asked 'Amr what Al-Hasan used to say regarding watermelons, Armenian cucumbers, cucumbers, roses, and that which does not come out all at once. He said: He used to say, "Do not buy except that which comes out all at once."