City of God

But we, for our part, have no manner of doubt that to increase and multiply and replenish the earth in virtue of the blessing of God, is a gift of marriage as God instituted it from the beginning before man sinned, when He created them male and female,— in other words, two sexes manifestly distinct. And it was this work of God on which His blessing was pronounced. For no sooner had Scripture said, “Male and female created He them,” than it immediately continues, “And God blessed them, and God said unto them, Increase, and multiply, and replenish the earth, and subdue it,” etc.

And though all these things may not unsuitably be interpreted in a spiritual sense, yet “male and female” cannot be understood of two things in one man, as if there were in him one thing which rules, another which is ruled; but it is quite clear that they were created male and female, with bodies of different sexes, for the very purpose of begetting offspring, and so increasing, multiplying, and replenishing the earth; and it is great folly to oppose so plain a fact. It was not of the spirit which commands and the body which obeys, nor of the rational soul which rules and the irrational desire which is ruled, nor of the contemplative virtue which is supreme and the active which is subject, nor of the understanding of the mind and the sense of the body, but plainly of the matrimonial union by which the sexes are mutually bound together, that our Lord, when asked whether it were lawful for any cause to put away one's wife (for on account of the hardness of the hearts of the Israelites Moses permitted a bill of divorcement to be given), answered and said, “Have ye not read that He which made them at the beginning made them male and female, and said, For this cause shall a man leave father and mother, and shall cleave to his wife, and they two shall be one flesh? Wherefore they are no more two, but one flesh. What, therefore, God has joined together, let not man put asunder.” It is certain, then, that from the first men were created, as we see and know them to be now, of two sexes, male and female, and that they are called one, either on account of the matrimonial union, or on account of the origin of the woman, who was created from the side of the man. And it is by this original example, which God Himself instituted, that the apostle admonishes all husbands to love their own wives in particular.