Who was the first to say, "Peace be upon you and the mercy of Allah and His blessings"?

The first to say "Peace be upon you and the mercy of Allah and His blessings" was Adam, peace be upon him. Allah Almighty commanded him to greet the angels, so he greeted them by saying, "Peace be upon you." They responded to him by adding "and the mercy of Allah," and thus this became the greeting of Adam and his descendants.