Hadith 982:4
Hajjaj narrated to us, he said: I heard Shu'bah narrating from Qatadah, who said: I heard al-Hasan narrating from Sa'd ibn 'Ubadah, that his mother died, so he said: "O Messenger of Allah, my mother has died, so shall I give charity on her behalf?" He said: "Yes." He said: "Then which charity is best?" He said: "Providing water." He said: So that is the water-dispensing place of the family of Sa'd in Medina.
حدثنا حجاج قال: سمعت شعبة يحدث، عن قتادة قال: سمعت الحسن، يحدث، عن سعد بن عبادة، أن أمه ماتت فقال: يا رسول الله، إن أمي ماتت فأتصدق عنها؟ قال: " نعم ". قال: فأي الصدقة أفضل؟ قال: " سقي الماء " قال : فتلك سقاية آل سعد بالمدينة