Is mutual agreement permissible for accepting a superior item of a different type in lieu of the stipulated item?
Chapter on Guaranteed Salaf (Advance Payment) for a Specified Term
Al-Mughni
Book of Sales
Primary text
If both parties mutually agree to accept an item of a different type in place of the stipulated item, it is permissible. This is because both items belong to the same genus, where exchanging one for the other with a surplus is prohibited, but they are combined for Zakat. Therefore, accepting one for the other is permissible, similar to the case within a single type.
Supporting text
Some followers of Al-Shafi'i hold that acceptance is not permissible based on the reasoning that prevented the obligation of acceptance in the first place. Ibrahim stated that one should not accept anything exceeding their Salam contract in measure or quality.