When is a promise binding religiously and judicially, and what is the difference between a binding promise and a Ju'alah (stipulated reward)?

A promise is a notification of the future delivery of good. It has been commanded to fulfill it. Scholars have differed as to whether it is legally binding (qada'an) or religiously binding (diyanatan). The more preponderant view is that it is always religiously binding, and legally binding if the promisee incurs a burden because of it. As for جعالة (ju’alah - a contract for a reward for a specific task), it is a contract for a known work in exchange for compensation. It differs from a promise in that it is a contract for work, unlike a promise which is a notification that does not require work from the promisee. Also, جعالة requires the compensation to be known, unlike a promise.