“The blessedness of communion with God is enjoyed in and heightened by the communion of saints. On earth already this communion is a wonderful benefit of faith.
Those who for Jesus’s sake have left behind house or brothers or sisters or father or mother or wife or children or fields already in this life receive houses, brothers, sisters, mothers, children, and fields—along with persecutions—(Mark 10:29–30), for all who do the will of the Father are Jesus’s brother and sister and mother (Matt. 12:50).
Through the mediator of the New Testament, believers enter into fellowship, not only with the militant church on earth, but also with the triumphant church in heaven, the assembly of the firstborn, the spirits of the righteous made perfect, even with innumerable angels (Heb. 12:22–24).
But this fellowship, though in principle it already exists on earth, will nevertheless be incomparably richer and more glorious when all dividing walls of descent and language, of time and space, have been leveled, all sin and error have been banished, and all the elect have been assembled in the new Jerusalem.
Then will be fully answered the prayer of Jesus that all His sheep may be one flock under one Shepherd (John 10:16; 17:21). All the saints together will then fully comprehend the breadth and length and height and depth of the love of Christ (Eph. 3:18–19).
They will together be filled with all the fullness of God (Eph. 3:19; Col. 2:2, 10), inasmuch as Christ, Himself filled with the fullness of God (Col. 1:19), will in turn fill the believing community with Himself and make it His fullness (πληρωμα, plērōma; Eph. 1:23; 4:10).
And sitting down at one table with Abraham, Isaac, and Jacob (Matt. 8:11), they will unitedly lift up a song of praise to the glory of God and of the Lamb. (Rev. 4:11; 5:12)”
–Herman Bavinck, Reformed Dogmatics: Holy Spirit, Church, and New Creation, Vol. 4, Ed. John Bolt, and Trans. John Vriend, (Grand Rapids, MI: Baker Academic, 2008), 4: 722–723.