Answer: The first man or Adam is the soul. When we speak about him, we do not refer to a physiological body in any way since it does not exist. We are speaking about a desire that basically wants to resemble the Creator.
This general desire spread from the world of Ein Sof (Infinity) downward through all the worlds: Adam Kadmon, Atzilut, Beriya, Yetzira, and Assiya. After passing through the filters of these worlds, the remaining desire became similar to the Creator under the influence of the upper Light. This is First Man, Adam HaRishon.
At the same time, there is the snake inside him—a desire that doesn’t want to resemble the Creator. It was intentionally created this way so that we will always be able to measure ourselves and determine where we are in the range between the Creator and the snake, which is the total opposite from the Creator, at which point and how far from the Creator or the snake we are.
These are the 125 levels of a person’s ascent up the spiritual ladder; the snake is at the bottom and the Creator at the top.
From the Kabbalah Lesson in Russian 5/14/17