Sahih al-Bukhari 12
صحيح البخاري#12SahihNarrated 'Abdullah bin 'Amr: A man asked the Prophet (ﷺ) , "What sort of deeds or (what qualities of) Islam are good?" The Prophet (ﷺ) replied, 'To feed (the poor) and greet those whom you know and those whom you do not Know (See Hadith No)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 2:5