“Let us be clear, then, that the basis for fellowship with other Christians is the fellowship we have with God through Christ. This is the emphasis in 1 John 1:3, ‘That which we have seen and heard we declare to you, that you also may have fellowship with us; and truly our fellowship is with the Father and with His Son Jesus Christ.’ The supernatural quality of the relationship Christians have with each other is because of what we share in Christ.
Commenting on this passage, John MacArthur wrote, ‘Anybody in fellowship with Jesus Christ is also in fellowship with anybody else in fellowship with Jesus Christ. This is our common ground. It is not social, economic, intellectual, cosmetic, or anything else superficial. Our common ground is that which is pulsing through the life of every Christian- the heartbeat of God. Our common ground is that we possess a common eternal life and are children in the same family.’” “Spiritual Disciplines Within the Church” Donald Whitney