The word "soul" here is being translated from the Greek word, ψυχή (psychē), which means, according to the lexicon, "the vital force which animates the body and shows itself in breathing" and "the seat of the feelings, desires, affections, aversions." The lexicon goes further to say, "the soul as an essence which differs from the body and is not dissolved by death (distinguished from other parts of the body)."
This means that the "soul" Jesus is speaking of is not just an organ or the moral part of the body as many make it out to be. The soul is who we are. We are each a soul.
This is confirmed by Jesus in another statement:
"Do not be afraid of those who kill the body but cannot kill the soul." (Matt. 10:28)If we are these physical bodies, then why would killing the body not be important to Jesus? Because these physical bodies are temporary vehicles. They are not who we are.
We are wearing these physical bodies much as a person wears clothes. And we are driving these physical bodies much as a person drives a car.
The fact that we were given these physical bodies as we fell from the spiritual realm is also confirmed in the Book of Genesis:
The LORD God made garments of skin for Adam and his wife and clothed them. (Genesis 3:21)
What are "garments of skin"? Is this speaking of animal skins or something? As if God went around and killed some animals and made fur coats for Adam and Eve?
Don't be ridiculous. This is metaphorically describing that the Supreme Being gave us these physical bodies.
But why? So that we could play out our self-centeredness. We became self-centered. This is the "forbidden fruit" that Adam and Eve - symbolizing each of us who fell to the physical world - ate.
You see, the spiritual realm is a place of love for the Supreme Being and love for the Supreme Being's children and playmates. Once we became self-centered, we had to leave. We were no longer qualified to stay in the spiritual realm.
"A man" - translated from the Greek word ἄνθρωπος (anthrōpos) - indicates a person occupying the physical body.
Whereas, once again, "soul" is taken from ψυχή (psychē), referring to the person within - our real spiritual selves.
The symbolism that Jesus is using relates to forgetting ones spiritual identity - ones relationship with the Supreme Being - in order to achieve material success in the physical world. To give up ones relationship with the Supreme Being means to identify oneself as the center of the universe, and everything revolves around me.
This is the height of self-centeredness, a condition that is also referred to as evil.
(For a translation of Jesus' statements from the Book of Matthew without institutional sectarian influence, see the Gospels of Jesus - translated from the original Greek texts.)