(Give to one) who is on the right, then again who is on the right.  

أَنَّ رَسُولَ اللَّهِ ﷺ أُتِيَ بِلَبَنٍ قَدْ شِيبَ بِمَاءٍ وَعَنْ يَمِينِهِ أَعْرَابِيٌّ وَعَنْ يَسَارِهِ أَبُو بَكْرٍ فَشَرِبَ ثُمَّ أَعْطَى الأَعْرَابِيَّ وَقَالَ الأَيْمَنَ فَالأَيْمَنَ  

The Apostle of Allah (may peace he upon him) came to Medina when I was ten years old and he died when I was twenty years old. My mother exhorted me to serve him. He (the Holy Prophet) came to our house, and we ruined a flabby goat for him and mixed it (the milk) with water from the well of the house. Messenger of Allah ﷺ drank that. Umar and Abu Bakr on his left side said to him: Messenger of Allah, give it to Abu Bakr, but he (the Holy Prophet) gave it to the desert Arab who was on his right. Messenger of Allah ﷺ said: He who is on the right, then he who is on the right.  

قَدِمَ النَّبِيُّ ﷺ الْمَدِينَةَ وَأَنَا ابْنُ عَشْرٍ وَمَاتَ وَأَنَا ابْنُ عِشْرِينَ وَكُنَّ أُمَّهَاتِي يَحْثُثْنَنِي عَلَى خِدْمَتِهِ فَدَخَلَ عَلَيْنَا دَارَنَا فَحَلَبْنَا لَهُ مِنْ شَاةٍ دَاجِنٍ وَشِيبَ لَهُ مِنْ بِئْرٍ فِي الدَّارِ فَشَرِبَ رَسُولُ اللَّهِ ﷺ فَقَالَ لَهُ عُمَرُ وَأَبُو بَكْرٍ عَنْ شِمَالِهِ يَا رَسُولَ اللَّهِ أَعْطِ أَبَا بَكْرٍ فَأَعْطَاهُ أَعْرَابِيًّا عَنْ يَمِينِهِ وَقَالَ رَسُولُ اللَّهِ ﷺ الأَيْمَنَ فَالأَيْمَنَ  

Messenger of Allah ﷺ came to our house and he asked for a drink. We milked a goat for him and then mixed it (the milk) with the water of this well of mine. I gave it to Messenger of Allah ﷺ and he drank it, while Abu Bakr was on his left and 'Umar was in front of him, and a desert Arab was on his right. When Messenger of Allah ﷺ had finished the drink, Umar said: Messenger of Allah, here is Abu Bakr, give him to drink; but Messenger of Allah ﷺ gave it to the desert Arab and he left out Abu Bakr and Umar. And Messenger of Allah ﷺ said: Those on the right, those on the right, those on the right (deserve preference). Anas said: This is the Sunnah, this is the Sunnah, this is the Sunnah.  

أَتَانَا رَسُولُ اللَّهِ ﷺ فِي دَارِنَا فَاسْتَسْقَى فَحَلَبْنَا لَهُ شَاةً ثُمَّ شُبْتُهُ مِنْ مَاءِ بِئْرِي هَذِهِ قَالَ فَأَعْطَيْتُ رَسُولَ اللَّهِ ﷺ فَشَرِبَ رَسُولُ اللَّهِ ﷺ وَأَبُو بَكْرٍ عَنْ يَسَارِهِ وَعُمَرُ وُجَاهَهُ وَأَعْرَابِيٌّ عَنْ يَمِينِهِ فَلَمَّا فَرَغَ رَسُولُ اللَّهِ ﷺ مِنْ شُرْبِهِ قَالَ عُمَرُ هَذَا أَبُو بَكْرٍ يَا رَسُولَ اللَّهِ يُرِيهِ إِيَّاهُ فَأَعْطَى رَسُولُ اللَّهِ ﷺ الأَعْرَابِيَّ وَتَرَكَ أَبَا بَكْرٍ وَعُمَرَ وَقَالَ رَسُولُ اللَّهِ ﷺ الأَيْمَنُونَ الأَيْمَنُونَ الأَيْمَنُونَ قَالَ أَنَسٌ فَهِيَ سُنَّةٌ فَهِيَ سُنَّةٌ فَهِيَ سُنَّةٌ  

Do you permit me to give it to them (the old men), but that boy said: by God. I will not give preference at your hand over me in my share. He (the narrator) said that Messenger of Allah ﷺ then gave it in his hand.  

أَنَّ رَسُولَ اللَّهِ ﷺ أُتِيَ بِشَرَابٍ فَشَرِبَ مِنْهُ وَعَنْ يَمِينِهِ غُلاَمٌ وَعَنْ يَسَارِهِ أَشْيَاخٌ فَقَالَ لِلْغُلاَمِ أَتَأْذَنُ لِي أَنْ أُعْطِيَ هَؤُلاَءِ فَقَالَ الْغُلاَمُ لاَ وَاللَّهِ لاَ أُوثِرُ بِنَصِيبِي مِنْكَ أَحَدًا قَالَ فَتَلَّهُ رَسُولُ اللَّهِ ﷺ فِي يَدِهِ  

This hadith is reported on the authority of Sahl b. Sa'd with a slight variation of wording.  

عَنِ النَّبِيِّ ﷺ بِمِثْلِهِ وَلَمْ يَقُولاَ فَتَلَّهُ وَلَكِنْ فِي رِوَايَةِ يَعْقُوبَ قَالَ فَأَعْطَاهُ إِيَّاهُ