Narrated Sahl bin Sa`d
A tumbler (full of milk or water) was brought to the Prophet (ﷺ) who drank from it, while on his right side there was sitting a boy who was the youngest of those who were present and on his left side there were old men. The Prophet (ﷺ) asked, "O boy, will you allow me to give it (i.e. the rest of the drink) to the old men?" The boy said, "O Allah's Messenger (ﷺ)! I will not give preference to anyone over me to drink the rest of it from which you have drunk." So, the Prophet (ﷺ) gave it to him.
Anas bin Malik said, that once a domestic sheep was milked for Allah's Messenger (ﷺ) while he was in the house of Anas bin Malik. The milk was mixed with water drawn from the well in Anas's house. A tumbler of it was presented to Allah's Messenger (ﷺ) who drank from it. Then Abu Bakr was sitting on his left side and a bedouin on his right side. When the Prophet (ﷺ) removed the tumbler from his mouth, `Umar was afraid that the Prophet (ﷺ) might give it to the bedouin, so he said. "O Allah's Messenger (ﷺ)! Give it to Abu Bakr who is sitting by your side." But the Prophet (ﷺ) gave it to the bedouin, who was to his right and said, "You should start with the one on your right side."