Marriage is one of those institutions which, although not of grace, but of nature, is yet adopted into the system of Christianity, and regulated by the rules which Christianity has laid down. The law of marriage has its origin in nature, and not in revelation; and yet the duties and rights connected with it, together with their exact nature and limits, are matters with which revelation deals. In so far as these involve moral or religious duties, we are to seek in the Bible for the code of law by which they are prescribed and determined. But marriage is, in another sense, a civil matter, coming under the province of the ordinary magistrate, and necessarily requiring to be dealt with in the way of civil enactment. There are civil rights intimately connected with it, in such a manner that the state cannot avoid the duty of legislating in regard to it, and regulating them by positive statutes and rules. In short, the institution of marriage is to be viewed in two lights, — either as a moral observance, falling to be regulated by the law of Scripture, or as a civil observance, falling to be regulated by the law of the state. And with this twofold character which it sustains, and this twofold legislation to which in every civilised and constituted society professing Christianity it is subjected, how, it may be asked, is a collision between the spiritual and the civil enactments on the subject — fraught, as it inevitably would be, with deadly consequence to the peace, if not the existence, of human society — to be avoided or prevented. If the state recognise the Bible as the Word of God, and the law of the Bible as the law of God, then it will take that law as the guiding principle for its own legislation, and make the enactments of the magistrate in regard to marriage coincident with the enactments of Scripture. But if the state do not recognise the Bible as the Word of God, there can be no security that its regulations shall not come into conflict with the regulations of Scripture as regards the institution of marriage, in such a manner as to put in peril not only the peace and purity of domestic life, but also through these the highest and holiest interests of human society. The ordinance of the family lies at the very foundation of civil society. It is the unit of combination around which the wider and more public relations of civil life associate themselves. Destroy or unhinge the domestic ordinances, unloose or unsettle the family bond, and no tie will be left holy enough or strong enough to bind up the broken and disjointed elements of human life.
James Bannerman, The Church of Christ.