And know that these who are reincarnated together in one body (with a new Neshama) as we described, it only happens when all of them are from the same source, in the secret of what is said, "וגאל את ממכר אחיו." Even though this (body) is a new Nefesh (it is the first time it is in the world), and even though it did not sin with some sin that the other souls who are reincarnated with it have done, with all of this it [the new soul] is more 'pnimiut' that all the others, as if it is at the level of 'veins and sinues' (which connect different body parts, just as it [the new soul] connects the other souls that come with it in the body).
Each of the souls in the body are from the same part of Adam HaRishon, and the source of their souls can be from the bones, the sinues, or the flesh. If they are from the flesh, this is worse [lower level] than souls coming from the veins or sinues. This new soul comes to clean the difficult blemishes that were done by the sins of the earlier Nefashot, and this [rectification of this place on the the body of Adam haRishon where all the souls from this same soul source come] bring down life force to the entire source [of that part of the spiritual body where those souls are coming from].