"When you tell someone “Assalamu Alaykom (Peace be upon you)”, you are telling them “My guarantee to you is not harm, I will never do anything to harm you.” SubhanAllah. What a powerful greeting it is! And yet we take it for granted. We don’t even think what we are saying when we say it. And may Allah (SWT) protect us from the times we become hypocritical. We tell somebody “Assalamu Alaykom”, without realizing that we have just told them we won’t harm them. And as soon as they turn their backs, we begin to harm them."
Mufti Menk (Islamic greetings (please watch !!))