… that in the dispensation of the fullness of the times He might gather together in one all things in Christ, both which are in heaven and which are on earth – in Him. (Ephesians 1:10)
Christ, the incarnate God, is the one in whom all things in heaven and earth are united. All the divisions, separations, alienations which had occurred in the cosmos as a result of sin are overcome in Jesus the Lord. This is high theology which shows us the cosmic and universal salvation which Christ has accomplished. Christ, by whom all things were made (Nicene Creed), as One Person of the Holy Trinity brought all things into existence and then restores all things which had become subject to sin and death. Christ is the healer not only of humans but of all creation. St Cyril of Alexandria (d. 444AD) comments:
As I said above, human nature, right at the beginning of the race in Adam, became subject to death and sin, and is redeemed in no other way except through Christ alone, for, as his disciple wrote, ‘There is no other name under heaven given among men by which we must be saved‘ (Acts 4:12). For it was necessary that he, through whom all things were brought into existence (John 1: 3 and Colossians 1:16), should become the restorer of what was corrupted, to nullify the debilitating effects of sin, to do away with pain, and also to bestow richly that good estate upon those who have come unto being through him . . . .
For in Christ, God the Father has brought together the things in heaven and the things upon earth under one head. What had fallen into an unseemly condition is raised back up to its first estate. It is only through Christ, then, that those things which had intruded into creation are now gone into nothingness, and that those things upon the earth are being restored into a renewed creation. For in him there is ‘a new creation‘ (2 Corinthians 5:17), and this word is true. (GLAPHYRA ON THE PENTATEUCH Volume 1, pp 65-66)
In the beginning, Jesus the Word of God, creates heaven and earth. But Christ does not remain in heaven, exterior to and over creation, for the Word became flesh as God enters into creation through the incarnation. Christ thus saves us and creation from within, now reuniting heaven and earth, the divine and the human, Creator and creation, the living and the dead, saints and sinners. All things are united in Christ which is the plan of salvation of the God who is love.