Muwatta Malik, Book 36, Hadith 1434 (In-Book)

Malik related to me from Abu'r-Rijal Muhammad ibn Abd ar-Rahman from his mother Amra bint Abd ar-Rahman that she informed him that the Messenger of Allah, may Allah bless him and grant him peace, said, "Do not withhold the surplus water of a well from people."

وَحَدَّثَنِي مَالِكٌ، عَنْ أَبِي الرِّجَالِ، مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ عَنْ أُمِّهِ، عَمْرَةَ بِنْتِ عَبْدِ الرَّحْمَنِ أَنَّهَا أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ يُمْنَعُ نَقْعُ بِئْرٍ ‏" ‏ ‏.‏

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also referenced under: Book 36, Hadith 30 (USC-MSA)