Sahih Muslim Book 23, Hadith Number 4983.

Chapter : It is good to drink milk.

Abu Bakr Siddiq reported: As we went along with Allah’s Messenger (may peace be upon him) from Mecca to Medina, we passed by a shepherd and Allah’s Messenger (may peace be upon him) was feeling thirsty. He (Abu Bakr Siddiq) said: I milked for him a small quantity of milk (from his goat) and brought it to him (the Holy Prophet), and he drank it and I was very happy.