The whole body, joined and knit together by what every joint supplies
– Ephesians 4:16 –
You by yourselves are not the church, and you must not keep on saying “we” if you are not doing anything in connection with your church. You must consider yourself as a distinct individual, and your first concern in the sight of God must be yourself. The body is made up of many bones, tendons, muscles, veins, arteries, and so on, and each one has its special place and function. In the same way, each of you has a particular position and role in the collective body that is called by the name “church.”
Think of your individuality, and think of it like this: you really are united to the body. It does not matter how beautiful a member may be if it is not in the body, for it is not where it should be, and it is not where it will be of any service. Imagine an eye that has just been taken from a dead body. It lies there on the operating table. What would you give for it? It is worth nothing, and it must be put out of sight, for it is useless. There is a finely formed ankle, but it is useless apart from the rest of the body. How beautiful that leg is! Yes, but because it is not joined to a body, you must bury it out of sight.…
I believe that every Christian should be joined to some visible church. That is his plain duty according to the Scriptures. God’s people are not dogs that can go about one by one. No, they are sheep, and therefore they should be in flocks. If I meet a man, all by himself, snapping at everybody—I may be called unloving, but I would hardly think that he was a sheep. I would be afraid that he was a dog. But when I see a man who associates with his fellow men, eats with them, takes delight in their company, and draws near with them to the Great Shepherd of souls, I say to myself, “I think he must be one of the sheep, for that is how sheep act.” So, beloved, you should go in flocks or companies—that is to say, you should be joined to some Christian church.
From Spurgeon on Unity, pp. 52, 53