Sahih Bukhari
Sahih Bukhari Volume 008, Book 074, Hadith Number 253B.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 74. Asking Permission
Narated By 'Abdullah bin ‘Amr: A man asked the Prophet, "What Islamic traits are the best?" The Prophet said, "Feed the people, and greet those whom you know and those whom you do not know."