Hodge: nature of the church III - 2 Abrahamic covenants

It is to be remembered that there were two covenants made with Abraham. By the one, his natural descendants through Isaac were constituted a commonwealth, an external, visible community. By the other, his spiritual descendants were constituted a Church. The parties to the former covenant were God and the natiofi; to the other, God and his true people. The promises of the national covenant were national blessings; the promises of the spiritual covenant, (i.e. of the covenant of grace,) were spiritual blessings, reconciliation, holiness, and eternal life. The conditions of the one covenant were circumcision and obedience to the law; the condition of the latter was, is, and ever has been, faith in the Messiah as the seed of the woman, the Son of God, and the Saviour of the world. There cannot be a greater mistake than to confound the national covenant with the covenant of grace, and the commonwealth founded on the one with the Church founded on the other.

When Christ came "the commonwealth" was abolished, and there was nothing put in its place. The Church remained. There was no external covenant, nor promises of external blessings, on condition of external rites and subjection. There was a spiritual society with spiritual promises, on the condition of faith in Christ. In no part of the New Testament is any other condition of membership in the Church prescribed than that contained in the answer of Philip to the eunuch who desired baptism: "If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God."-Acts viii. 37. The Church, therefore, is, in its essential nature, a company of believers, and not an external society, requiring merely external profession as the condition of membership. While this is true and vitally important, it is no less true that believers make themselves visible by the profession of the truth, by holiness of life, by separation from the world as a peculiar people, and by organizing themselves for the worship of Christ, and for mutual watch and care. The question, when any such organization is to be regarded as a portion of the true Church, is one to which the Protestant answer has already been given in a few words, but its fuller discussion must be reserved to some other occasion. (Princeton Review, October 1853).