Sahih Bukhari Volume 9, Book 90, Hadith 6964

حَدَّثَنَا إِسْمَاعِيلُ، حَدَّثَنَا مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يُمْنَعُ فَضْلُ الْمَاءِ لِيُمْنَعَ بِهِ فَضْلُ الْكَلإِ ‏"‏‏.

Narrated By Abu Huraira : Allah's Apostle said, "One should not prevent others from watering their animals with the surplus of his water in order to prevent them from benefiting by the surplus of grass."