Hadith 857

Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, 'A rider should greet a pedestrian; a pedestrian should greet one who is sitting; and a small group should greet a large group (of people).''

[Al-Bukhari and Muslim].

The narration in Al-Bukhari adds: The Messenger of Allah (PBUH) said, "The young should greet the elderly.''