Allah The Exalted says: When you are greeted with a greeting, greet in return with what is better than it.

Abdullah bin Amr (RA) �narrated : A man asked The Prophet (SAW) "Whose Islam is better" The Prophet � replied, "To feed (others), and say salam to whom you recognize and (also) whom you do not recognize."

Abu Huraira (RA) narrated: Allah's Messenger (SAW) said, "You will not enter Paradise until you believe; and you will not believe until you love one another. Shall I not guide you to a thing which if you do, you will love one another: spread (the greeting of peace) Salaam amongst yourselves."
 

AbuUmamah (RA) narrated: Allah's messenger (RA) said," "Indeed the person nearest to Allah The Exalted is the one who is foremost in them in offering Salam."
 

Abu Hurrairah (RA) narrated : Allah's messenger (SAW) said," The younger person should greet the older one, and the walking person should greet the sitting one, and the smaller number of people should greet the larger number of people."
 

Abu Hurairah (RA) narrated: The Messenger of Allah (SAW) said, "A rider should greet a pedestrian, a pedsestrian should greet one who is sitting, and a small group should greet a large group (of people)."
 

Anas bin Malik (RA) narrated, that the Messenger of Allah (SAW) passed by some children and greeted them.

Anas (RA) narrated that The Prophet (SAW) used to visit the Ansar and greet their children and patted / touched their heads.

Anas bin Malik (RA) said : O Messenger of Allah (SAW) "Should we bow down for others? He � said No. We said," should we embrace one another?" He (SAW) said: No, but you should shake hands with one another.

Al Bara (RA) narrated: Allah's messenger (SAW) said, "Two muslims will not meet and shake hands without having their sins forgiven before they depart."