It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "Allah Almighty created Adam (peace be upon him) with a height of sixty cubits. Then He commanded him: Go and greet that group of angels who are sitting. Listen carefully to the reply they give you, for that will be your greeting and the greeting of your descendants. So he said: «السلام علیکم»! The angels replied: «السلام علیک ورحمۃ اللہ»! They added «ورحمۃ اللہ». Every person who enters Paradise will be of this stature. Since then, the stature of mankind has been decreasing continuously."
Benefits and Issues: Salam (greeting of peace) is a Sunnah that was taught right at the beginning of creation after the creation of Adam. Its existence has remained in all divinely revealed religions. From the very beginning of humankind, this has been the prescribed method, which the Westernized class has replaced with "hello" and "bye"—a great deprivation.
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 978