Sahih Bukhari Volume 002, Book 026, Hadith Number 700.
Narated By Ibn Abbas : Allah's Apostle came to the drinking place and asked for water. Al-Abbas said, "O Fadl! Go to your mother and bring water from her for Allah's Apostle." Allah's Apostle said, "Give me water to drink." Al-Abbas said, "O Allahs Apostle! The people put their hands in it." Allah's Apostle again said, 'Give me water to drink. So, he drank from that water and then went to the Zam-zam (well) and there the people were offering water to the others and working at it (drawing water from the well). The Prophet then said to them, "Carry on! You are doing a good deed." Then he said, "Were I not afraid that other people would compete with you (in drawing water from Zam-zam), I would certainly take the rope and put it over this (i.e. his shoulder) (to draw water)." On saying that the Prophet pointed to his shoulder.