It is narrated from Abdullah bin Amr (may Allah be pleased with him) that a man asked the Messenger of Allah (peace and blessings be upon him): "Which (manners) of Islam are the best?" He replied: "(That) you feed (others), and you greet with peace both those whom you know and those whom you do not know." Agreed upon.
Hadith Referenceمشكوة المصابيح / كتاب الآداب / 4629
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 (6236) و مسلم (39/63)»