Sahih Muslim Book 7, Hadith Number 3018.

Chapter : It is essential to stay (for two or three nights) at Mina during the days of Tashriq (11th, 12th and 13th) and exemption from this command for the suppliers of water.

Bakr b. ‘Abdullah al-Muzani said: While I was sitting along with Ibn ‘Abbas (Allah be pleased with him) near the Ka’ba, there came a bedouin to him and said: What is the matter that I see that the progeny of your uncle supply honey and milk (as drink to the travellers), whereas you supply al-nabidh (water sweetened with dates)? Is it due to your poverty or due to your close-fistedness? Thereupon Ibn ‘Abbas said: Allah be praised, it is neither due to poverty nor due to close-fistedness (but due to the fact) that Allah’s Apostle (may peace be upon him) came here riding his she-came, and there was sitting behind him Usama. He asked for water, and we gave him a cup full of nabidh and he drank it, and gave the remaining (part) to Usama; and he (the Holy Prophet) said: You have done Food, You have done well. So continue doing like it So we do not like to change what Allah’s Messenger (may peace be upon him) had commanded us to do.