In his first epistle, John said,
What we have seen and heard we proclaim to you also, that you also may have fellowship with us; and indeed our fellowship is with the Father, and with His Son Jesus Christ. (1 John 1:3 nasb)
In other words, the gospel is an invitation from the Godhead for us to share the fellowship that the Father and Son share with one another. The Greek word for fellowship is koinonia. It is an important word in New Testament Greek that literally means, “sharing in common.” So, fellowship is sharing in common. We are invited to share the same relationship that God the Father and God the Son have together. One thing is clear about this relationship: God the Father and God the Son have everything in common. Neither withholds anything from the other.
In John 17:10, Jesus said to His Father,
And all [things that are] mine are thine, and thine are mine. (kjv)
That’s perfect koinonia, perfect fellowship—the perfect sharing of all things. It is the perfect pattern of relationship into which God wants to bring us.