Sahih Bukhari Volume 3, Book 43, Hadith Number 631.
Narated By Sahl bin Sad As-Sa’idi : A drink (milk mixed with water) was brought to Allah’s Apostle who drank some of it. A boy was sitting to his right, and some old men to his left. Allah’s Apostle said to the boy, “Do you allow me to give the rest of the drink to these people?” The boy said, “O Allah’s Apostle! I will not give preference to anyone over me to drink the rest of it from which you have drunk.” Allah’s Apostle then handed the bowl (of drink) to the boy. (See Hadith No. 541).