Sunan Ibn Majah, Volume 5, Book 33, Hadith 3684 (DarusSalam) ⓘ
It was narrated that Sad bin Ubadah said: "I said: 'O Messenger of Allah, what charity is best?' He said: 'Giving water to drink.'"
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، عَنْ هِشَامٍ، صَاحِبِ الدَّسْتَوَائِيِّ عَنْ قَتَادَةَ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ سَعْدِ بْنِ عُبَادَةَ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ أَىُّ الصَّدَقَةِ أَفْضَلُ قَالَ " سَقْىُ الْمَاءِ " .
also referenced under: Hadith 3684 (Reference) & Book 33, Hadith 28 (In-Book)