Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that milk mixed with water was brought to the Messenger of Allah (peace and blessings be upon him). On his right was a Bedouin and on his left was Sayyiduna Abu Bakr (may Allah be pleased with him). The Prophet (peace and blessings be upon him) drank the milk and handed the remainder to the Bedouin, and said: "The one on the right, so the one on the right (takes precedence)." And in another narration: "Those on the right, so those on the right. Beware! Always begin from the right side."