Musannaf Ibn Abi Shayba 13:109

Zayd ibn al-Hubab narrated to us, from Sawadah ibn Habban, who said: I heard Muhammad ibn Sirin, and he was asked about two men, one of whom bought food and the other was with him. He said: "I have witnessed the sale and the taking of possession." Then he [the second man] said: "Take a profit from me and give it [the food] to me." He [Ibn Sirin] said: "No, not until the two measures (sa's) pass through it, so that its increase is yours and its decrease is upon you."