ENOfficial
It was narrated from Sa'd bin 'Ubadah that his mother died. He said: "O Messenger of Allah, my mother has died; can I give charity on her behalf?" He said: "Yes." He said: "What kind of charity is best?" He said: "Providing drinking water." And that is the drinking-fountain of Sa'd in Al-Madinah.
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنِي إِبْرَاهِيمُ بْنُ الْحَسَنِ، عَنْ حَجَّاجٍ، قَالَ سَمِعْتُ شُعْبَةَ، يُحَدِّثُ عَنْ قَتَادَةَ، قَالَ سَمِعْتُ الْحَسَنَ، يُحَدِّثُ عَنْ سَعْدِ بْنِ عُبَادَةَ، أَنَّ أُمَّهُ، مَاتَتْ فَقَالَ يَا رَسُولَ اللَّهِ إِنَّ أُمِّي مَاتَتْ أَفَأَتَصَدَّقُ عَنْهَا قَالَ " نَعَمْ ". قَالَ فَأَىُّ الصَّدَقَةِ أَفْضَلُ قَالَ " سَقْىُ الْمَاءِ ". فَتِلْكَ سِقَايَةُ سَعْدٍ بِالْمَدِينَةِ.
sunnah.com