Wa’ad is the most fundamental building block of Islamic theory of exchange. It is an undertaking/promise to do something, and in general is unbinding in its nature. It may become binding only once the promisee has undertaken some action pursuant to having received the promise. When a party A promises to buy something (e.g., a car) from another Party B on a future date T1, the promise becomes or may become binding when Party B has actually bought the car, say, from someone else or from the market, and decides to call upon the promise given by Party A. In this sense, there is an optionality built in giving and taking of promises. This sophisticated characteristic of Wa’ad makes it a very useful tool for product structuring.