Is it permissible for the seller to increase the price of a commodity when deferring payment compared to cash payment, and what is the ruling on this in light of usurious transactions?

It is permissible to sell a commodity for a deferred price higher than its current cash price, whether the payment is in installments or a single payment at the due date, provided that the seller and buyer agree on the type of sale (cash or deferred) before parting ways. This increase is not usury (riba), and the Shari'ah has not specified a fixed amount for it. However, the Prophet, peace and blessings be upon him, encouraged leniency in buying and selling.

However, if the sale was made for a specified price and the buyer wishes to delay payment, it is not permissible for the seller to increase the price in exchange for this delay; otherwise, that would be prohibited usury.