What is the ruling on benefiting from a bank guarantee that is non-negotiable (not convertible to cash), by reserving it for the benefit of another party for a specified period in exchange for a sum of money, or by permanently assigning it to another party in exchange for a sum of money?

The guarantor's relinquishment of their guarantee to another is permissible, but it is not permissible to take compensation for it. This is because guaranteeing is a contract of benevolence (irfaq), not one of exchange (mu'awadat), whether the relinquishment is temporary or permanent. Jurists have stipulated the impermissibility of taking compensation for suretyship (kafalah), as it resembles a loan that brings benefit, which is forbidden by Islamic law.