The oneness of the Triune God is testified in New Jerusalem by one throne, one river, one tree, and one light. The city also testifies God’s fullness, in three gates on each of the four sides to open the city to every corner of the earth, and in the tree of life bearing twelve fruits for our eternal nourishment.
The three of the Triune God are one by dwelling in each other; this is coinherence. Through death and resurrection the Lord Jesus brought us into the same relationship with God (but not into His Godhead). In John 14:20 He told us that in resurrection we “will know that I am in My Father, and you in Me, and I in you.”
The Lord prayed that we would all participate in this oneness— “That they all may be one; even as You, Father, are in Me and I in You, that they also may be in Us; that the world may believe that You have sent Me….I in them, and You in Me, that they may be perfected into one, that the world may know that You have sent Me and have loved them even as You have loved Me” (John 17:21, 23).
Our oneness is in the Triune God. This oneness will be fully displayed by New Jerusalem. But God desires that oneness also be displayed now, “that the world may believe” and “that the world may know.” We can pray with the Lord that we be perfected into one, not waiting for New Jerusalem but now that the world may know God’s doings.