Narrated Abu Huraira:
The Prophet (ﷺ) 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.”
Sahih al-Bukhari 6231

Narrated Abu Huraira:
Allah’s Messenger (ﷺ) said, “The riding one should greet the walking one, and the walking one should greet the sitting one, and the small number of persons should greet the large number of persons.”
Sahih al-Bukhari 6232