Maliks Muwatta Book 31, Hadith Number 42.

Section : Buying on Delayed Terms and Re-Selling for Less on More Immediate Terms.

Yahya related to me from Malik from Nafi that Abdullah ibn Umar said, “In the time of the Messenger of Allah, may Allah bless him and grant him peace, we used to buy food. He sent orders for us to move our purchases from the place in which we purchased them to another place before we re-sold them.”