Is it permissible to benefit from discount coupons before purchase, or from cash-back offers (Rebate) after purchase, which have a specific validity period? Is it permissible to combine two discount offers for the same product if one is from the manufacturer and the other from the seller? And is it permissible to benefit from a discount coupon before purchase in addition to a discount offer after purchase, even if the product's price becomes very low or free with money earned in rare cases?

There is no harm in utilizing coupons if the discount is applied at the time of purchase, provided that the product is permissible to acquire and that the utilization adheres to the stipulated conditions. As for utilization after purchase, in addition to the aforementioned, it is stipulated that it should not be a stratagem for usurious borrowing. For instance, if the price of the commodity paid by the buyer is higher than its market price, and the buyer then reclaims this difference after a period, augmented by the seller's discount. It is permissible to combine the benefit of a discount at the time of purchase and afterward, if there is no condition preventing it.