Section: If one reconciles with a man for the conveyance of his rainwater from his roof onto his [roof, or onto his land from his roof], or onto his land from his land, it is permissible if that from which the water flows is known, either by observation or by knowing its dimensions, because water differs according to the smallness or largeness of the roof, and it is impossible to regulate it otherwise. It is a condition to know the location from which the water flows onto the roof because that varies. It does not require mentioning a duration because need dictates this, and it is permissible to contract over the usufruct at the location of need without it being specified, as in marriage. The owner of the water does not own the conduit because he does not thereby receive the usufruct of the conduit permanently, nor for most of the duration, unlike the watercourse. They also differ in that the water in the watercourse does not need to be measured because the measurement of that is achieved by measuring the watercourse, as he does not possess the right to convey through it more than its capacity of water; whereas water from the roof requires knowing the measurement of the roof because a little or a lot may flow from it. If the roof upon which the water flows is leased or is a loan (ariya) in someone’s possession, it is not permissible to reconcile for conveying water onto it, because he is harmed by that and was not granted permission for it, so he may not dispose of it; unlike water in a pre-dug watercourse, for the land is not harmed by it. If the roof water flows onto land, it is possible that it is not permissible for him to reconcile for that, because if it requires digging, it is not permissible for him to dig on another's land, and because he creates a right for other than the owner of the land, so he might claim entitlement to that against its owner. It is also possible that it is permissible if it does not require digging and there is no harm in it, because it is in the position of conveying water into a pre-dug watercourse. It is not permissible except for a period that does not exceed the duration of his lease, as we said regarding the conveyance of water in the watercourse. And Allah knows best.