According to (Anabaptist) Conrad Grebel, the church was not to be found in the bishop's multitudes, nor in the "partially" reformed state church of the Protestant Reformation. Rather, it was "the few who believed and lived right." It was a fellowship of people who held each other mutually accountable and who covenanted together to follow their Lord. Biblically, this concept is found in Mt. 18, where Jesus speaks of the "two or three gathered together" in his name. When they so gather, they have the power to meaning to reject or accept behaviors (ethics) and that the results of the deliberations that they conduct in this manner will be honored by God. In Mt. 16, the term "bind and loose" appears again, this time in the context of the church having the "keys to heaven." In Acts 15 there is an example of such an assembly, and we are told (Acts 15:28) that the result of their meeting is "good with the Holy Spirit and with us." This is the biblical basis of the house church doctrine of church: it is only when believers meet in the company of other believers, put aside their own agendas and ambitions, and open themselves to the Holy Spirit, that can they properly hear the voice of their king, the living Christ, as he now sits at the right hand of the Father and rules his Kingdom. Always persecuted by authority figures, the early house church people felt that the Holy Spirit spoke most clearly to the group. Because this corporate process is centered in a desire to be obedient to Christ, God honors the decisions made in this manner.
House church theology says that the work of the church is to co-operate with God (1 Cor. 3:9). This means that 1 Cor. 13-15, Rom. 12-14, and Eph. 4 (the "spiritual gifts" passages) are intended not as general statements of Christian behavior or of individual gifting, but are intended to instruct local churches (house churches) in proper behavior, to appropriate spiritual gifts in a corporate context, to appreciate the gifts of fellow brothers and sisters, to manifest other behaviors that make the church an effective outpost of the Kingdom of God on earth, and, especially, to love each other within the church fellowship (the proper context for interpreting 1 Cor. 13). So the house church doctrine of church centers on gathered people, never the individual, the denomination, or the "universal church" (which has no real biblical basis at all). When Paul speaks of it is always the local church to which he is referring.
When the people of a house church gather, it is not properly a mere group of individuals that walks through a liturgy or receives grace from a treasury administered by human agents. Rather, it is an assembly of believers that comes together as part of the "family" of God (Eph. 3:15) for fellowship, mutual support, and to further the agenda of God. The relationships that are to be built within that family are to prepare us for an eternity with God and to be a model for our own, biological families in this fallen world.
A Final Caveat
One more thing needs to be said about the church. This doctrine was a costly one, thousands of martyrs having paid the ultimate price. When one reads Lk. 12:51-3, Mt. 5:11-12, and many other passages, one sees that the believer's life is not expected to be an easy one. In Jn. 13, when he realized that "the Father had put all things under his power," Jesus' response was to wash his disciples feet. We get this doctrine not so much from the text of the early Anabaptist and Baptist confessions--we get it from the manner that those confessions were made. Believers huddled together and decided whether to give in to the powers that oppressed them or to carry on and take the consequences of continuing their struggle against the state church and its minions. It was true in those days, and it is true in the underground churches in the world today--where the church suffers, it is strong. When the church relaxes in comfort and ease, it declines.
