O Messenger of Allah, ’Umm Sa‘d died. Which charity is the best?" He said: 'Water.' He said: So, he dug a well and said: "This is for ’Umm Sa‘d

The mother of Sa‘d ibn ‘Ubādah (may Allah be pleased with him) passed away, and he asked the Prophet (may Allah's peace and blessings be upon him) about the best types of charity to give on behalf of his mother. He (may Allah's peace and blessings be upon him) told him that the best charity is water. So, he dug a well and made it a charity on behalf of his mother.