The relationship between spirit, mind and body is similar to the relationship between steam, water and ice. All three are phases of the same basic reality.
Steam is a loosely bonded gaseous reality made up of molecules with two hydrogen molecules and one oxygen (H2O). As this gas cools it condenses into water, which is simply the same molecules more closely knit into a liquid. Water is steam, which has less freedom of movement; it cannot defy gravity as steam does.
When the water is cooled even more it begins to crystallize and becomes ice, which is made up of the same molecules (H2O), but now they are so tightly attached to each other that they cannot move at all in relationship to each other. There is much more rigidity and much less freedom. Ice is water (or steam actually) with less freedom.
In the same way, we can imagine that Spirit «condenses» to become mind. That mind is spirit with less freedom of movement. And that our body is “crystallized mind” (or actually, then, crystallized spirit) which has much less freedom of expression than the mind or the spirit. The mind then is spirit manifested on the mental level, and the body is spirit manifested on the material level.
Imagine that you have an incredibly large, say infinitely large room full of steam (spirit) which becomes condensed into water droplets, which gather into small, pools (minds). Imagine then that there is a freeze and that each small pool freezes and that we have millions of different ice-forms (bodies).
Each ice-form has a completely different shape, color and other characteristics. Each piece of ice is unique. It is a unique expression of the specific pool (mind) from which it crystallized.
Yet all the pools and thus all the ice-forms have been condensed from one universal infinitely large cloud of steam. In this way we can understand that all of the forms of all beings are simply manifestations of the One Universal Spirit.
The next time you are walking down the street, or riding the bus or in a gathering of people, look around you and remember that you and all these other beings are «condensations» of the same universal spirit.