أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ، قَالَ حَدَّثَنَا وَكِيعٌ، عَنْ هِشَامٍ، عَنْ قَتَادَةَ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ سَعْدِ بْنِ عُبَادَةَ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ إِنَّ أُمِّي مَاتَتْ أَفَأَتَصَدَّقُ عَنْهَا قَالَ ‏"‏ نَعَمْ ‏"‏‏.‏ قُلْتُ فَأَىُّ الصَّدَقَةِ أَفْضَلُ قَالَ ‏"‏ سَقْىُ الْمَاءِ ‏"‏‏.‏

It was narrated that Sa'd bin 'Ubadah said: "I said: 'O Messenger of Allah, my mother has died; shall I give in charity on her behalf?' He said: 'Yes.' I said: 'What kind of charity is best?' He said: 'Providing drinking water.'" Translation Not Available

Book Ref: Sunan An Nisai Book 30 Hadith 3664
Web Ref:  Sunan An Nisai Vol 4 Book 30 Hadith 3694