It was narrated from ‘Abdullah bin ‘Amr that a man asked the Messenger of Allah (peace be upon him):

“O Messenger of Allah, which (aspect) of Islam is the best?” He said: “Offering food (to the needy) and greeting with Salam those whom you know and those whom you do not know.”

(Ibn Majah Vol. 4, Book 29, Hadith 3253)