As for exchange (mu'awada), it is for him to acknowledge a physical object in his possession or a debt under his liability, and then they agree to compensate him for it with something for which compensation is permissible. This is of three types: The first is that he acknowledges one of the two monetary types (gold or silver) and reconciles [on] the other; for example, if he acknowledges that he owes him one hundred dirhams and reconciles with him for ten dinars, or acknowledges ten dinars and reconciles on one hundred dirhams. This is a currency exchange (sarf), for which the conditions of sarf must be met, such as taking possession during the session and the like. The second is that he acknowledges commodities and reconciles with him for currency, or acknowledges currency and reconciles with him for commodities; this is a sale, and the rulings of sale apply to it. If he acknowledges a debt and reconciles it for a specified (described) item under liability, it is not permissible to separate before taking possession, because it is selling debt for debt. The third is that he reconciles with him for the residence of a house, the service of a slave, or the like, or for him to perform a specific task; this is a lease (ijara), which has the same rulings as all other leases. If the house or the slave is destroyed before any of the benefit is enjoyed, the lease is annulled, and he receives back what he reconciled with. If it is destroyed after some of the benefit has been enjoyed, it is annulled regarding the remainder of the period, and he receives back the portion of the remainder. If he reconciles with him to marry his slave girl, and he is someone for whom it is permissible to marry slave women, it is valid, and the object of reconciliation serves as her dower (sadaq). If the marriage is annulled before consummation by something that causes the dower to lapse, the husband receives back what he reconciled with; if he divorces her before consummation, he receives back half of it. If the one who acknowledges is a woman and she reconciles with the claimant by marrying herself to him, it is permissible. If the acknowledged item was a defect in her sold property and she reconciles with him through marriage, it is valid. If the defect is removed, she receives back its compensation (arsh), because that is her dower, so she receives it back, not her marriage dower (mahr al-mithl). If the defect is not removed, but her marriage is annulled by something that causes her dower to lapse, he receives back the compensation (arsh) from her.