Okay, one source of confusion here is that these words "soul" and "spirit" get used by different traditions and teachings in different ways. Very often what one source says is explicitly contradicted by another source! So you need to check with each tradition means by those words.

In the system I use, human beings have three bodies -- material, etheric, and astral -- and are evolving the fourth, which belongs to the mental plane. These are all bodies, and they do not belong to soul or spirit. The spirit consists of the seed forms of the bodies we haven't evolved yet -- the spiritual and causal bodies we'll evolve in the far future -- gathered around the Divine Spark. The soul is something else again: it's the collected experience of all our previous lives, all the way back to the beginning, which serves as a template for the spirit when it creates the bodies it will indwell in each new incarnation.