Promising or unilateral promising (wa’ad) is an undertaking or commitment issued by one party to the contract, known as the promisor, to the other party, called the promisee, (e.g., the purchaser/ reseller or the purchase orderer in murabaha to the purchase orderer). Shari’a (Islamic religious law) regards wa’ad as binding on the party who makes or extends it, unless a force majeure intervenes and hinders its fulfillment. However, a promise is binding from a shari’a perspective if it is contingent upon a cause and the promisee has incurred costs because of the promise.

Mutual or bilateral promising (muwa’adah) is a promise vis-à-vis another promise. For example, in murabaha to the purchase orderer associated with a binding mutual promise, if the purchaser (who was instructed to purchase an object) accepts the request of the instructing orderer, the contract of sale would be concluded after the object of sales becomes in the instructed purchaser’s possession. This sale, from a shari’a standpoint, is considered to be in fulfillment of the binding mutual promise between the two parties. When the purchaser offers the object to the orderer, the latter should accept it based on the binding mutual promise. As such, the contract of sale is formally established.

However, in trading in currencies, bilateral promising to purchase and sell currencies is impermissible by shari’a if the promise if binding, regardless of the purpose of trading (pure trading, hedging currency risk, etc). Yet, a unilateral promise (wa’ad), i.e., a promise from one party without the other, is permissible whether it is bonding or non-binding.