Greetings, charity, and the Hereafter

What is the principal command in «أَفْشُوا السَّلَامَ»?

Greetings, Family Ties, Charity, and Preparation for the Hereafter (Accounts 6–8)

• Greet only close friends
• Spread greetings of peace
• Give salam only at home
• Replace greetings with food