Sahih al-Bukhari 5619
Sahih al-Bukhari · Book 74: Drinks · The one on the right should drink first
Narrated Anas bin Malik:
حَدَّثَنَا إِسْمَاعِيلُ ، قَالَ حَدَّثَنِي مَالِكٌ ، عَنِ ابْنِ شِهَابٍ ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أُتِيَ بِلَبَنٍ قَدْ شِيبَ بِمَاءٍ، وَعَنْ يَمِينِهِ أَعْرَابِيٌّ وَعَنْ شِمَالِهِ أَبُو بَكْرٍ، فَشَرِبَ، ثُمَّ أَعْطَى الأَعْرَابِيَّ، وَقَالَ " الأَيْمَنَ الأَيْمَنَ " .
Milk mixed with water was brought to Allah's Messenger (ﷺ) while a bedouin was on his right and Abu Bakr was on his left. He drank (of it) and then gave (it) to the bedouin and said, 'The right" "The right (first).