On Exhortation To Chastity by Tertullian
Chapter V.--Unity of Marriage Taught by Its First Institution, and by the Apostle's Application of that Primal Type to Christ and the Church.
For the laying down of the law of once marrying, the very origin of the human race is our authority; witnessing as it emphatically does what God constituted in the beginning for a type to be examined with care by posterity. For when He had moulded man, and had foreseen that a peer was necessary for him, He borrowed from his ribs one, and fashioned for him one woman; whereas, of course, neither the Artificer nor the material would have been insufficient (for the creation of more). There were more ribs in Adam, and hands that knew no weariness in God; but not more wives in the eye of God. And accordingly the man of God, Adam, and the woman of God, Eve, discharging mutually (the duties of) one marriage, sanctioned for mankind a type by (the considerations of) the authoritative precedent of their origin and the primal will of God. Finally, |there shall be,| said He, |two in one flesh,| not three nor four. On any other hypothesis, there would no longer be |one flesh,| nor |two (joined) into one flesh.| These will be so, if the conjunction and the growing together in unity take place once for all. If, however, (it take place) a second time, or oftener, immediately (the flesh) ceases to be |one,| and there will not be |two (joined) into one flesh,| but plainly one rib (divided) into more. But when the apostle interprets, |The two shall be (joined) into one flesh| of the Church and Christ, according to the spiritual nuptials of the Church and Christ (for Christ is one, and one is His Church), we are bound to recognise a duplication and additional enforcement for us of the law of unity of marriage, not only in accordance with the foundation of our race, but in accordance with the sacrament of Christ. From one marriage do we derive our origin in each case; carnally in Adam, spiritually in Christ. The two births combine in laying down one prescriptive rule of monogamy. In regard of each of the two, is he degenerate who transgresses the limit of monogamy. Plurality of marriage began with an accursed man. Lamech was the first who, by marrying himself to two women, caused three to be (joined) |into one flesh.|