صَحِيحُ مُسْلِمٍ
Sahih Muslim 2029 a
The Book of Drinks
It is recommended to pass water and milk etc., to the right of the one who drinks first
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنِ ابْنِ شِهَابٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أُتِيَ بِلَبَنٍ قَدْ شِيبَ بِمَاءٍ وَعَنْ يَمِينِهِ أَعْرَابِيٌّ وَعَنْ يَسَارِهِ أَبُو بَكْرٍ فَشَرِبَ ثُمَّ أَعْطَى الأَعْرَابِيَّ وَقَالَ الأَيْمَنَ فَالأَيْمَنَ .
Anas b. Malik reported that there was brought to Allah's Messenger (ﷺ) a cup of milk mixed with water, while there was on his right a desert Arab and on his left Abu Bakr. He (the Prophet) drank; he then gave it to the desert Arab and said: (Give to one) who is on the right, then again who is on the right.
Sahih Muslim, 2029 aSahihصحيح