What keeps our resurrected eternal body functioning?
In the eternal state, the Spirit of God Himself keeps the resurrected, flesh-and-bone body functioning. Just as life is in the blood in this physical existence, in the eternal existence life will be in the Spirit, and the Spirit will take over the role blood now has.
Les explains that flesh and blood cannot inherit the Kingdom, but flesh and bone will. The question then is what life-giving substance will keep that eternal body functioning, and the answer is the Spirit—the Spirit of God Himself. Even now believers are indwelt by the presence of the Holy Spirit, but not to the degree that will be true in the eternal state. When we come into the eternal state of flesh and bone, the Spirit will actually take over the role that the blood now has. Life is in the blood in this physical existence, and in the eternal existence life is going to be in the Spirit. Les ties this to 1 Corinthians 15, where the last Adam, Christ, is a life-giving or quickening spirit, and he notes these deep doctrines of resurrection come from the same letter written to carnal believers.
And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit.