Sunan Ibn Majah
3253
Sahih+3

It was narrated from ‘Abdullah bin ‘Amr that a man asked the Messenger of Allah (ﷺ):“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.”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi