Al-Kāfi - Volume 2 > The One Who Must Offer the Greeting of Peace
Hadith #3

3ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ عَنْ عَلِيِّ بْنِ أَسْبَاطٍ عَنِ ابْنِ بُكَيْرٍ عَنْ بَعْضِ أَصْحَابِهِ عَنْ أَبِي عَبْدِ الله (عَلَيهِ السَّلام) قَالَ سَمِعْتُهُ يَقُولُ يُسَلِّمُ الرَّاكِبُ عَلَى الْمَاشِي وَالْمَاشِي عَلَى الْقَاعِدِ وَإِذَا لَقِيَتْ جَمَاعَةٌ جَمَاعَةً سَلَّمَ الأقَلُّ عَلَى الأكْثَرِ وَإِذَا لَقِيَ وَاحِدٌ جَمَاعَةً سَلَّمَ الْوَاحِدُ عَلَى الْجَمَاعَةِ.

3. A number of our people have narrated from Sahl ibn Ziyad from Ali ibn Asbat from ibn Bukayr from certain individuals of his people who has said the following: “I heard abu ‘Abd Allah (a.s.) saying, ‘A person riding should offer greetings of peace to the one walking, the one walking to the one stationary and sitting. On meeting a group the one in smaller numbers offers the greeting of peace to that in greater numbers and one person offers greetings of peace to a group.”’