(Read this twice, then think about it awhile!)
In 1 Jn. 1: John describes his fellowship with God as one dependent upon his walking "in the light" of God's truth. He had learned of Christ, first hand, and then wrote this truth for our benefit; so that we may have the same kind of fellowship he had, i.e., fellowship with God. There is no fellowship with God for those who walk in darkness—error and sin.
But in 3 Jn. (vs. 9-10) John tells us of some of his brethren (evidently folk who had fellowship with God) who had been cast out of the church. Diotrephes had severed fellowship with them, and forbad others to have such fellowship. This was wrong, undoubtedly; but the fact remains that it could and did happen. This is a case where God maintained a fellowship which men refused.
The opposite is true in 1 Cor. 5. Here, a member of the church in Corinth (whom we conclude to have had fellowship with God at one time) now lived in immorality. According to 1 Jn. 1: (and implied here) this man had now severed his fellowship with God. He walked in darkness. But the brethren in Corinth continued to keep fellowship with him. This, too, was wrong—but it did happen. Men maintained a fellowship which God refused.
Thus, two types of fellowship are apparent—that with God, depending wholly upon our walking in truth; and that with men (even brethren), which is subject to man's approval or disapproval. Saying we should approve only that which God approves (with which I agree) does not change facts. Brethren sometimes approve that which they should not—or disapprove that which they sould accept. God knows the difference, and judges accordingly; but the "party" doesn't always act as God would have it act.
As we individually obey the gospel we pledge ourselves to serve God. To Him we must individually give account when life is through. (Matt. 16:24;Rom. 14:4,12) Following this agreement of allegiance, and subject to its obligations, we join hands with others to work and worship together in a local fellowship, or congregation. God commands this union; the ties of this association are grand and its obligations real; but it remains the means of serving the Master, and must never become our Master.
Fellowship of men with men is an earthly tie which has an acceptable religious significance only when it compliments our service to God. It is given divine regulations, but men do not always follow those regulations. One who counts on the outward bond of "church" fellowship alone to guarantee his spiritual redemption, leans on a broken reed. NO, I DO NOT DEPRECIATE THE IMPORTANCE OF THE CHURCH. I seek to emphasize the meaning of the true church, as God's people, who do God's work, in God's way—praised for their allegiance and service to God, rather than for their faithfulness to the "party".
Brethren who are primarily interested in keeping their fellowship with God intact, will be drawn to one another by this common interest, and find a congregational fellowship that forecasts the sweetness of heaven.