It is forbidden to explicitly set two tiered pricing for sales, A lower price for cash payment & a higher price for credit (delayed) payment. The additional payment for credit is considered ribbis interest, as it is a payment for delaying the owed funds. (Mishnah BM 65b & Shulchan Aruch YD 173) Question: May a seller offer a reward on a sale, which he explicitly limits only to cash sales. Is the buyer's forfeiting the receipt of the reward in exchange for delayed payment considered ribbis?
NOTE: I am reffering to a situation where charging more for delayed payment would be FORBIDDEN. My question is whether forfeiting the receipt of a gift given for cash payments is considered ribbis. If a certain situation would allow charging more for credit (or credit cards), that is not in my question.