Hebrews 13:17 tells believers to “Obey your leaders and submit to them,” but how do you decide who your leaders are? 1 Peter 5:2 tells church leaders to “shepherd the flock that is among you,” but how do church leaders decide who they're supposed to shepherd?
The New Testament never clearly describes what we today understand as church membership, but it’s clearly implied. Peter told the elders “shepherd the flock that is among you.” They aren’t to shepherd every Christian they ever come across. Peter assumes that the elders know exactly who they are responsible for and who they will have to give an account to God about. The elders know who they are responsible for because they know exactly what people have committed themselves to their leadership. To fulfill their responsibility, the elders of a church must be a part of a church that has a clear membership list of people he is responsible to provide spiritual leadership for.
Peter tells the believers to shepherd the flock that is among them. God doesn’t envision Christians submitting to the leadership of one church on a Sunday morning one week, then another church on Wednesday night of that week, then another church the next Sunday morning. God calls us to commit ourselves to one body of believers and the leadership of that body of believers. If you’re a member of this church, the leaders of this church are responsible for you. If a believer is a member of one church, but they’re also regularly attending another church, that believer is making it difficult for the leadership of their church to be obedient in watching over their soul if they’re not fully committed to that church alone. This doesn’t mean that God gets angry at you if you visit another church with a friend every once in awhile. It simply means that you are committed to your church and not another.
Spiritual leaders care for the spiritual health of the members they are responsible for. They have to give an account to God for how well they’ve done this. Obeying and submitting to leaders means that you live lives that honor God, and if the leader is a genuine God-appointed leader, how to do that will be reflected in his teaching. Your leaders help you to understand what God is trying to communicate to you about your life. They don’t dictate God’s will to you, but they help you to understand how to hear and communicate with God yourself. Obeying and submitting also means that you understand and devote yourself to the vision God has given the leader of your church.
In Ephesians 4:16 Paul says that a church can’t grow the way it is supposed to if each member isn’t working properly. Every church member is important and serves a role in their church that the church suffers for if that member doesn’t fulfill their role. Church members cannot be only halfway committed to their church because both they and the church suffer if they do.
Although the New Testament never outlines the concept of church membership, the whole of the New Testament assumes that believers will commit themselves to one body of believers and exercise their gifts there. God has placed spiritual leaders over specific churches so that people will submit to the leadership of that church.