Bismillah Walhamdulillah Was Salaatu Was Salaam ‘ala Rasulillah
Narrated Abu Huraira (Radi-Allahu ‘anhu):
The Prophet (Sallallahu ‘Alaihi Wa Sallam) said, “The young should greet the old, the passer by should greet the sitting one, and the small group of persons should greet the large group of persons.”
Bukhari Vol. 8 : No. 250