Who are those who will be watered on the Day of Resurrection, and who will be in charge of watering?

Allah will quench the thirst of the believers in Paradise with whatever their souls desire, as mentioned in Surah Muhammad. The attribution of providing drink to Allah in His saying, "And their Lord will give them to drink a pure drink," is an attribution of grace and favor.

As for the Prophet Muhammad, peace and blessings be upon him, Allah bestowed upon him the Hawd (Pond) before the people of Paradise enter it. Its water is whiter than milk and its scent is more pleasant than musk, and its vessels are like the stars in the sky. Whoever drinks from it will never thirst again. Allah also bestowed upon him the river Al-Kawthar in Paradise. It has been reported that the Prophet, peace and blessings be upon him, will hand some of his Ummah drinks from the vessels, and this is an honor for some of His servants, while the rest of the Ummah will drink from the vessels of the Hawd.

There is no evidence that angels will quench the thirst of the believers. Rather, the people of Paradise will have servants who circulate among them with drinking vessels from pitchers and cups. These are immortalized youths, whom Allah described as "scattered pearls."