أَخْبَرَنَا أَبُو عَمَّارٍ الْحُسَيْنُ بْنُ حُرَيْثٍ، عَنْ وَكِيعٍ، عَنْ هِشَامٍ، عَنْ قَتَادَةَ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ سَعْدِ بْنِ عُبَادَةَ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ أَىُّ الصَّدَقَةِ أَفْضَلُ قَالَ سَقْىُ الْمَاءِ "
It was narrated that Sa'd bin 'Ubadah said:
"I said: 'O Messenger of Allah, what kind of charity is best?' He said: 'Providing drinking water.'"
Reference: Sunan an-Nasa'i 3665
In-book : Book 30, Hadith 55
English translation : Vol. 4, Book 30, Hadith 3695