Sayyiduna Sa'd bin Ubadah (may Allah be pleased with him) narrated: I said: "O Messenger of Allah, during her lifetime my mother used to give charity and spend from my wealth, and now she has died. Tell me, if I give charity on her behalf or free a slave on her behalf, may we hope for something for her?" He (peace and blessings be upon him) said: "Yes." He said: "O Messenger of Allah, guide me to a charity." He (peace and blessings be upon him) said: "Give water to drink." Al-Hasan (al-Basri) (may Allah have mercy on him) said: After that, the water jars of Sa'd (for giving people water to drink) remained constantly in Madinah.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5364