The alteration of the object of obligation in fulfilment of the obligation

The obligor may not compel the obligee to accept something other than the agreed object of the obligation، but they may agree that، in fulfilment of the obligation، another thing (property) which، by nature، differ or does not differ from the object of the obligation or with regard to quality or quantity، is equal، superior or inferior to it be delivered. In spite of different opinions، it appears that in this case، an anonymous contract is concluded that، in the same time، is the cause of satisfaction of the obligation and a separate cause for ownership.