I say, and with God's success: The situation will be that the bank bought this merchandise from the merchant and then sold the merchandise to you, and you became its owner, not the merchant. You have the right to dispose of it as you wish, whether selling it to the merchant or to anyone else without any obligation to anyone. If you sell it afterward to the merchant, it is valid and permissible. However, the issue is not that the merchandise belongs to the merchant while he hands you the check, but rather it is a trade with him or with someone else. However, there remains a suspicion that you told the bank you wanted to buy merchandise for construction and then you sold it. In the transaction, there is deception, and God knows best.