Does obligating the buyer in a Murabaha contract affect the validity of the contract, keeping in mind that canceling the purchase after requesting specifications might not be acceptable?

The agreement before the sale between the ordering party and the bank is a promise, not a sale. It is permissible to make it a binding promise, not a binding sale. If the client breaks his promise, the bank can claim from him the actual damages incurred. This obligation does not affect the validity of the Murabaha sale. The criterion for a binding promise in Murabaha is that there should be an option for both parties or one of them; otherwise, it would resemble the sale itself, and in that case, it is a condition that the seller owns the item being sold. To ensure the client's seriousness, banks take an advance payment called a "seriousness margin," which is permissible.