Romans 8:10-11 ESV
But if Christ is in you, although the body is dead because of sin, the Spirit is life because of righteousness. If the Spirit of him who raised Jesus from the dead dwells in you, he who raised Christ Jesus from the dead will also give life to your mortal bodies through his Spirit who dwells in you.
Life and death are strange companions in the earth of man. We have within us light and darkness which cohabit in a single entity. The life of the Spirit resides in these bodies of death. This is the field of testing and transformation which serves to refine us into the image of God. We are created in His image, but begin life rough and ill defined.
We will take our final form when we trade these mortal bodies for ones that will match our immortal souls. Our life in the Spirit serves as a guarantee of the inheritance that awaits.