Is it permissible for a merchant to buy large quantities of discounted goods and then sell them at their original price after the discount period ends, and what is the ruling on this action?

Trade is based on profit, and there is no limit to profit. Rather, it is permissible as long as the buyer and seller agree upon it, based on the Almighty’s saying: "Unless it be a trade by mutual consent from you," and the Prophet’s (peace be upon him) saying: "Indeed, selling is by mutual consent." Buying goods when they are cheap to sell them when their price rises is not considered forbidden hoarding. Forbidden hoarding is buying foodstuffs during times of high prices and withholding them to increase their value.