Hafiz Abdush Shakoor Tirmidhi
Benefits:
From the aforementioned hadith, it is understood that the deceased receive the reward of charity (sadaqah) that is given on their behalf after their death, whether or not the deceased had made a bequest (wasiyyah) for it. Similarly, if Hajj is performed on behalf of one's parents, its reward also reaches the parents.
In another narration, it is mentioned that Sayyiduna Sa'd ibn 'Ubadah radi Allahu anhu submitted: "O Messenger of Allah! My mother has passed away. Which charity is best?"
Bukhari, Kitab al-Wasaya, Bab Idha Waqafa Ardan al-Kh, No: 2770. Muslim, Kitab al-Wasiyyah, Bab Wusul Thawab al-Sadaqat ila al-Mayit, No: 1004. Sunan Abi Dawud, No: 2882. Sunan Tirmidhi, No: 669. Sunan Nasa'i, No: 3655. Sunan Ibn Majah, No: 2717.
The Prophet sallallahu alayhi wa sallam replied: "Water." It is thus understood that one should give such charity by which the reward continues to reach (the deceased) permanently, for example, an orchard or arranging for water. In earlier times, wells were of great importance.
If a water tank is constructed in a mosque, school (madrasa), or travelers' inn (musafir khana), or if arrangements are made to pay the water bill, these things also become a means of great reward.
Source: Musnad Ishaq bin Rahwayh, Page: 743