Is it permissible to extend the term in a Salam contract with the mutual consent of both parties?

It is permissible for the contracting parties in a forward contract (salam) to agree on expediting the delivery of the forward-purchased item (al-muslam fihi) before its initially agreed-upon time. The buyer is obligated to take possession of it if the seller presents it before its time, provided that its possession does not entail harm or alteration, such as forward-purchased items made of iron, lead, oil, honey, and the like.