Paul's analogy of church as a body and of yourself as hand. If you don't attach to a body of believers and receive spiritual blood, oxygen, and nutrients from the body  you will die. "Whatever happens, conduct yourselves in a manner worthy of the gospel of Christ. Then, whether I come and see you or only hear about you in my absence, I will know that you stand firm in the one Spirit, striving together as one for the faith of the gospel". Philippians 1:27