The term "church," as used in our subject, must necessarily be understood to mean the assembly of persons converted to God by the hearing of the Gospel of Jesus Christ, proclaimed by himself, founded and organized by him into a covenant body of worshipers during his personal ministry on earth, with himself as the head. The body of which Jesus said, that the gates of hell should not prevail against it (Matt. 16:18). That organization which in the first centuries of its existence endured the severest persecutions, - even martyrdom; in which many of its most faithful adherents sealed their faith with their own life's blood. That body whose Chief Shepherd preserved a succession of faithful representatives of its doctrine, faith and love through the long, dark period of the Middle Ages; and nourished it through the years of the great Reformation of Martin Luther and others; and until it resumed its ancient organic form, in the year 1708, at Schwarzenau, Germany; of which Alexander Mack, Sr., wrote, saying: "We have, indeed, no new church, nor any new laws; but in simplicity and true faith we desire to remain with the old church which Christ instituted through his blood, and to follow the commandment which was from the beginning" [Mack's Writings, p. 138]. That body, which from this time on, has by regular succession expanded and developed into its present magnitude, as the General Assembly of the Church of the Brethren.
Source: Two Centuries of the Church of the Brethren