Musannaf Ibn Abi Shayba 13:38

Hammad ibn Abi Sulayman narrated to us, from Yazid al-Dalani, from Musa ibn al-Hurr, from Humayd ibn Abd al-Rahman, that a man paid in advance (salam) for dirhams, then he took some of it as wheat and some of it as dirhams. He said: "There is no harm in that; that is the recognized practice."