Praise be to Allah,
Sufyaan ibn ‘Uyaynah narrated to us from [Muhammad ibn Shihaab] az-Zuhree who said that he had heard Anas ibn Maalik say,
“The came to Madeenah [as an emigrant] when I was ten years old, and he passed away when I was twenty years old. My mother would urge me to serve him. [One day], he entered our house and we milked a sheep for him and mixed the milk with water from a well in the house [before we served it to him in a bow ]. A Bedouin was sitting on his right, Abu Bakr was on his left, and Umar was sitting somewhere there. After Allah’s Messenger (PBUH) had drunk, Umar said to him, ‘Give [the remaining milk] to Abu Bakr.’ But he gave it to the Bedouin instead and said, ‘ [Serve the person] on [your] immediate right first, then [serve ]the one next to him.'”
(Musnad Aflmad, Vol. 3, p. 11 0. The isnaad of this hadeeth is Saheeh according to the conditions set by al-Bukhaaree and Muslim.)
Source:
Thulaathiyyaat Musnad Ahmad ibn Hanbal (may Allah have mercy on him)
Reports of Imaam Ahmad that have only three narrators between him and the Prophet, peace, and blessings be upon him.
Shaykh Muhammad ibn Ahmad ibn Saalim as–Saffaareenee al–Hanbalee ~(1114 –1188 AH)