Arabic and Islam
It is easy to see the influence of Islam in the Arabic language, especially in greetings and other phrases. The prophet Muhammed admonished his followers to be kind and to return kindness with more kindness. Thus, came about the formula for Arabic greetings: the original greeting expresses kind wishes, and the reply expresses even more. One should also note that much of the wording used in greetings is religious in nature.
Before we leave the subject of religion and greetings, we want to remind you of something that Alif Baa points out concerning the greeting as-salaamu calaykum السلام عليكم. This greeting is particularly Islamic in nature, so you will hear it more among Muslims than non-Muslims.