WHY FELLOWSHIP IS RESTRICTED?
We are “Endeavoring to keep the unity of the Spirit in the bond of peace. There is one body, and one Spirit, even as ye are called in one hope of your calling; one Lord, one faith, one baptism, one God and Father of all, who is above all, and through all, and in you all,” Ephesians 4:3-6.
This highlights the importance of being united in our worship of God. (Reading the whole chapter would be beneficial.)
Sharing of the emblems of bread and wine is a command of Christ, and is restricted to those professing the principles of our faith. Every professional career has a series of fundamentals that form the basis of the discipline. Doctors, lawyers, electricians and every career must agree to the principles of the respective trade or association.
It is not enough to say “I believe in the God of the Bible” in order for fellowship to have it’s benefit. See also 1 Corinthians 1:10 and 1 Corinthians 12:13.
Our communion identifies us as members of the one Body, associated in Christ and there can be no communion of light with darkness: 1 Corinthians10:16, Ephesians 4:16-18, 2 Corinthians 6:14-17, Deuteronomy 7:2-6, Ephesians 5:11.