Sahih Bukhari, Chapter: Distribution of Water

Once a tumbler (full of milk or water) was brought to Allah's Apostle (SAW) 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 (SAW) asked, "O boy ! Do you allow me to give (the drink) to the elder people (first)?" The boy said, "I will not prefer anybody to have my share from you, O Allah's Apostle (SAW)!" So, he gave it to the boy.