Is the merchant obligated to reduce the agreed-upon price in installment sales with an increase if the buyer pays before the specified time?

There is no objection to taking the full price from someone who expedites the repayment of a debt before its due date. However, dropping a portion of the debt in exchange for prompt payment, without any prior condition or request, is permissible. If, however, this occurs through collusion, stipulation, or request, the majority of scholars prohibit it. This is the issue of "forgo and expedite" (ضع وتعجل), which some Companions and early Muslims disliked and considered a form of usury (riba).