Sunan at-Tirmithiy كتاب البيوع باب ما جاء فى بيع فضل الماء
The Prophet, peace and blessings of God be upon him said, “Surplus water (1) should not be withheld in order to prevent pasture (2).” Footnotes: (1) i.e. water exceeding the need of well owners. (2) If the animals are not allowed access to the water, they will not graze in that area. Click on ḥadīth to read more