In the early church, one thing Cyprian stressed over and over is the importance of Christians being united with an assembly of other Christians (a.k.a. a/the church). Some Christians were tempted to leave the assembly because of persecution; others were tempted to leave because some sect was pulling them away. Today, the reasons for Christians not uniting publicly with other Christians are many. I’m sure you’ve all heard different excuses why people don’t join a local church. By the way, my favorite excuse is “the church is full of hypocrites,” which is an hypocritical statement itself. I like what John Crotts writes on this topic.
“The Lord Jesus intended for every one of his children to be connected to one of these local churches. There are no examples of free-floating Lone Ranger saints in the New Testament. …While there is no single verse in the Bible commanding, ‘Thou shalt join a church,’ a clear inside or outside relationship of an individual Christian and a local church is nevertheless apparent. When Hebrews 13:17 calls upon individual believers to ‘obey your leaders and submit to them, for they are keeping watch over your souls,’ it is assumed that you know who your leaders are, that you are making their lives joyful by following their leadership, and that they know who you are, since they must give an account for your soul.”
“In Matthew 18:15-17, as Jesus spells out the steps of church discipline to restore a sinning brother, the final two steps are 1) to tell it to the church and then, if there is still no repentance, 2) to put the person out of the church, treating him as the Jews treated Gentiles and tax collectors. Once again, it is assumed that you are inside a local church where you are being held accountable for your words and actions. Then, if you don’t repent, you are put out of the body you must have previously been in.”
“Whether a church calls this relationship ‘membership’ is not nearly as important as the fact that the body has a clear way of knowing which Christians are inside and which are outside the church. When Christians wanting to live the Christian life outside the local church claim that their church membership in the universal church is sufficient, they are missing many facets of God’s design for the local church.”
These quotes can be found on page 45 of Crotts’ book, Loving the Church: God’s People Flourishing in God’s Family.