Sahih Bukhari Volume 7, Book 74, Hadith 5614

حَدَّثَنَا عَبْدَانُ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا يُونُسُ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ أَنَّهُ رَأَى رَسُولَ اللَّهِ صلى الله عليه وسلم شَرِبَ لَبَنًا، وَأَتَى دَارَهُ فَحَلَبْتُ شَاةً فَشُبْتُ لِرَسُولِ اللَّهِ صلى الله عليه وسلم مِنَ الْبِئْرِ، فَتَنَاوَلَ الْقَدَحَ فَشَرِبَ، وَعَنْ يَسَارِهِ أَبُو بَكْرٍ وَعَنْ يَمِينِهِ أَعْرَابِيٌّ، فَأَعْطَى الأَعْرَابِيَّ فَضْلَهُ، ثُمَّ قَالَ ‏"‏ الأَيْمَنَ فَالأَيْمَنَ ‏"‏‏.‏

Narrated By Anas bin Malik : I saw Allah's Apostle drinking milk. He came to my house and I milked a sheep and then mixed the milk with water from the well for Allah's Apostle. He took the bowl and drank while on his left there was sitting Abu Bakr, and on his right there was a bedouin. He then gave the remaining milk to the bedouin and said, "The right! The right (first)."