Bro. Foy E. Wallace, Jr. once made the observation that it takes more than a single harness to work a team of horses. One need not be an old-time farmer to see the sense in that. There must be some means of common direction and guidance if a plurality of horses, people, or churches are to work as one, hence "harness to fit the team."
In the days of the "harness shed" one might determine how a man worked his horses by looking at the gear. If a man with four horses had four single harnesses, we would conclude that he worked his horses independently. But if we found double harnesses, or gear for larger teams, we would draw conclusions accordingly.
A Look Into God's Harness Shed
There is ample evidence in the NT that God intended for saints to work together in local churches (1 Cor. 1:2) and God has a harness for this type of team. The elders (or bishops) are overseers in the Lord's church (Acts 20:28) and the means by which saints are treated as a unit. (Acts 11:30) We may study the realm of elders, the scope of their oversight, and learn the extent to which God intended to "team" the saints.
Acts 14:23 reads, "And when they had ordained them elders in every church—." We have long recognized this passage as teaching that each congregation is independent and self-ruled; i.e., has its own direction and guidance system. This is a single harness (one group of elders) to rule only one church. Every other passage on the subject confirms this conclusion. Titus was to "ordain elders in every city–." (Titus 1:5) Peter wrote, "Feed the flock of God which is among you, taking the oversight thereof,—" (1 Pet. 5:1-3) When Paul wrote to the church at Philippi he addressed "all the saints — with the bishops and deacons." (Phil. 1:1) God's harness shed contains no gear whereby two or more churches may be teamed to work as one on any project.
Making Harness Where God Made None
But men have never been satisfied with God's plan. It seems to them the churches should be hitched together–they speak of "sister" churches, in a "brotherhood of churches". Since God gave no harness for such, they must make their own. Some use a permanent hook-up, with churches organically related through a synod, national headquarters, etc.; while others use various agencies whereby churches may "team up" for benevolent or "mission" projects. A "board" or "sponsoring church" agrees to oversee and coordinate the work, and hence becomes the harness whereby many churches work as one. However the matters are handled, a harness has been devised which God did not authorize.
This error is not corrected by accusing those who object of being "anti" benevolent or mission work; nor by saying the Bible says "go" but it doesn't say "how". God DOES SAY HOW TO ORGANIZE, and the independent local church is the whole of it. God's harness fits the only team God authorized. It is enough for the faithful.