a sale concluded by exchange without a verbal formula, and similar leases that customary practice recognizes as sales and leases, holds that such a contract is valid whether concluded by himself or by others. Whoever considers it invalid considers it invalid whether concluded by himself or by others.

Thus, if the trustee acting as lessor holds either of these two views, he must abide by it, whether it works to his advantage or against him. If he considers this contract invalid, he may neither hand over the leased property, demand the stipulated rent, nor [prevent] (1) the tenants from leaving. He would be like someone who hands property over to a usurper: he would be liable for whatever perishes while in the possession of the person who has taken control, just as if he had handed over his own property under an invalid contract that he himself considers invalid.

If, however, he considers this contract valid, he may hand over the property and demand the stipulated rent. He may not accept a higher offer over that of the tenant, nor evict him before the lease expires without a ground recognized by Islamic law that warrants rescission.

Whenever the trustee insists on treating the contract as invalid with respect to the tenant, valid with respect to himself, and nonbinding with respect to the tenant, he is unjust and oppressive. This impugns his fitness to serve as trustee and his uprightness. He must lease whatever he lets under a valid lease. By agreement of the Muslims, he may not enter into a lease that he knows to be invalid. And Allah knows best.