Mysteries of the Qabalah, by Elias Gewurz, , at sacred-texts.com
The word according to the secret tradition designates the deep interior feeling binding an entity to its own individual existence, making it ardently desire to preserve and enlarge it.
Nachash, the snake within man is the radical egotism which causes an individual being to make of itself a center and to relate everything else to it. Moses defines this sentiment as the seducing passion of elementary nature and the secret spring with which the Creator has provided all (animate) things in nature; we know it by the name of natural instinct. Nachash is not to be understood as a separate being, but rather as a central movement given to matter, a hidden spring acting in the depths of things.
The self-seeking elements within man, the blind passions common to us all in our early stages of evolution are the offspring of this snakeNachash. This word stands
for an unreasoning self-centered instinct in all the oriental languages, it means an internal ardour, a centralized fire, agitated by a violent movement and seeking to extend itself. The Chaldaic derives from it all ideas of fear, sorrow, anxiety and evil, and painful passions. In the Arabic, Syriac and Ethiopian it signifies a tormenting affliction.
All love emotions are expansive, all emotions of hatred are restrictive.
Hope and faith are of the nature of love and expand the soul, while fear and doubt and despair are of the nature of hate and contract our souls, making us feel uneasy, and unhappy. The snake stands for contraction, for tightness and indrawing; while men fight and quarrel with one another they always resemble more or less the old snake, each drawing to its side, anxious for self-preservation. Freedom from the snake's anguish can only be had by ceasing from the snake's ways, and learning to obey the law of love, the first dictate of which is self-sacrifice.