Maliks Muwatta Book 31, Hadith Number 53.

Section : General Section on Selling Food.

Yahya related to me from Malik that Muhammad ibn Abdullah ibn Abi Maryam asked Said ibn al-Musayyab’s advice. “I am a man who buys food with receipts from al-Jar. Perhaps I will buy something for a dinar and half a dirham, and will be given food for a half.” Said said, “No. You give a dirham, and take the rest in food.” (A half dirham did not exist as a coin.)