Thus, he permitted him to irrigate his garden from a privately owned river without the owners’ permission. This indicates that the owner is obliged to make its surplus available for crops.

In the narration of al-Barzāṭī, he said concerning a man who owned land but had no well on it, while his neighbor had a well on his own land: “The well-owner may not prevent his neighbor from watering his land from that well.” The first narration is more correct: he is obliged to make the surplus available for livestock, but not for crops.

Abū Hurayrah narrated that the Messenger of Allah (peace and blessings be upon him) said: “Whoever withholds surplus water in order to prevent access to surplus pasture by means of it, Allah will withhold His mercy from him on the Day of Resurrection.”

Making this surplus available is subject to four conditions. The first is that the water remain in the well. Once he has drawn it, he is not obliged to give it away, and he may sell it. The second is that it be connected to pasture where livestock graze. If it is not near pasture, he is not obliged to make it available.

The third is that the livestock have no other water available to them. If they find other water that is freely available, he is not obliged to make his water available, and the livestock must turn to the freely available water. If the other available water is privately owned, each of the two water-owners is obliged to make the surplus of his water available to whoever comes to it. Once the livestock have enough from the surplus of either water source, the obligation falls away from the owner of the other.

The fourth is that the livestock’s coming to his water not cause him any harm, whether to his crops or his livestock. If their coming would cause him harm, they are to be prevented, while the herders may draw the surplus water for them.

When these four conditions are fulfilled, he is obliged to make the surplus available, and it is unlawful for him to charge anything for it. If these conditions are not fulfilled, he may charge for it when selling it, provided that it is sold by a quantity measured by volume or weight. It may not be sold without measurement, nor may it be sold according to an amount defined by watering livestock or crops.

Aḥmad said in the narration of Abū Ṭālib: “If he has a well in his house and allowing people access to it would inconvenience him, there is no harm in his preventing them. But if he has a place where he collects rainwater, he must not prevent one who fears thirst.” Thus, he exempted him from making the surplus available when doing so would cause him harm.

In the narration of Ṣāliḥ, he said: “He may not withhold the surplus from one who asks for it if they have nothing with which to water their livestock, for he would thereby be withholding something that is freely available.” Thus, he took into consideration whether they could find any other water.

If a person digs a well and thereby acquires ownership of it and its protected surrounding area, and someone then digs another well, diverting the water of the first well into it so that it drains away, or digs it for ritual purification and thereby alters the water of the first well, must the second well be filled in or not? There are two narrations. According to one of them, it is allowed to remain and its owner is not prevented from using it. Aḥmad stated this explicitly in the narration of Abū ʿAlī al-Ḥasan ibn Thawwāb, concerning a man who dug a well in his house, after which another man dug a well in his own house beside the dividing wall between them, causing the latter well to draw away the water of the former. He said: “Do not block this well because of that one. This one lies within its owner’s property.”