Abu Huraira (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "The rider should greet the one who is walking, the one who is walking should greet the one who is sitting, and the smaller group should greet the larger group." Agreed upon.
Hadith Referenceمشكوة المصابيح / كتاب الآداب / 4632
Hadith Gradingالألبانی:مُتَّفَقٌ عَلَيْهِ | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (6232) و مسلم (2160/1)»