Leviticus 18:6

6.None of you shall approach to any that is near. This name does not include all female relations; for cousin-ger-mans of the father’s or mother’s side are permitted to intermarry; but it must be restricted to the degrees, which He proceeds to enumerate, and is merely a brief preface, declaring that there are certain degrees of relationship which render marriages incestuous. We may, therefore, define these female relations of blood to be those which are spoken of immediately afterwards, viz., that a son should not marry his mother, nor a son-in-law his mother-in-law; nor a paternal or maternal uncle his niece, nor a grandfather his granddaughter, nor a brother his sister, nor a nephew his paternal or maternal aunt, or his uncle’s wife, nor a father-in-law his daughter-in-law, nor a brother-in-law his brother’s wife, nor a step-father his stepdaughter. The Roman laws accord with the rule prescribed by God, as if their authors had learnt from Moses what was decorous and agreeable to nature. The phrase which God uses frequently “to uncover the turpitude,” is intended to awaken abhorrence, in order that the Israelites may beware more diligently of all incest. The Hebrew word, indeed, ערוה, gnervah, signifies nakedness, therefore some translate it actively, “the nakedness of thy father,” i e. , the womb which thy father hath uncovered; but this meaning would not be suitable to the nakedness of thy daughter, or thy daughter-in-law, or thy sister. Consequently, there is no doubt but that Moses means to denote that it is a filthy and shameful thing.

We must remember, what I have already hinted, that not only are incestuous connections out of wedlock condemned, but that the degrees are pointed out, within which marriages are unlawful. It is true, indeed, that this was a part of the political constitution which God established for His ancient people; still, it must be borne in mind, that whatever is prescribed here is deduced from the source of rectitude itself, and from the natural feelings implanted in us by Him. Absurd is the cleverness which some persons but little versed in Scripture pretend to, (87) who assert that the Law being abrogated, the obligations under which Moses laid his countrymen are now dissolved; for it is to be inferred from the preface above expounded, that. the instruction here given is not, nor ought to be accounted, merely political. For, since their lusts had led astray all the neighboring nations into incest, God, in order to inculcate chastity amongst his people, says; “I am the Lord your God, ye shall therefore keep my statutes; walk not after the doings of the land of Egypt and of Canaan;” and then He adds what are the degrees of consanguinity and affinity within which the marriage of men and women is forbidden. If any again object that what has been disobeyed in many countries is not to be accounted the law of the Gentiles, the reply is easy, viz., that the barbarism, which prevailed in the East, does not nullify that chastity which is opposed to the abominations of the Gentiles; since what is natural cannot be abrogated by any consent or custom. In short, the prohibition of incests here set forth, is by no means of the number of those laws which are commonly abrogated according to the circumstances of time and place, since it flows from the fountain of nature itself, and is founded on the general principle of all laws, which is perpetual and inviolable. Certainly God declares that the custom which had prevailed amongst the heathen was displeasing to Him; and why is this, but because nature itself repudiates and abhors filthiness, although approved of by the consent (suffragiis) of men? Wherefore, when God would by this distinction separate His chosen people from heathen nations, we may assuredly conclude that the incests which He commands them to avoid are absolute pollutions. Paul, on a very trifling point, sets before our eyes the law of nature; for, when he teaches that it is shameful and indecorous for women to appear in public without veils, he desires them to consider, whether it would be decent for them to present themselves publicly with their heads shorn; and finally adds, that nature itself does not permit it. (1 Corinthians 11:14.) Wherefore, I do not see, that, under the pretext of its being a political Law, (88) the purity of nature is to be abolished, from whence arises the distinction between the statutes of God, and the abuses of the Gentiles. If this discipline were founded on the utility of a single people, or on the custom of a particular time, or on present necessity, or on any other circumstances, the laws deduced from it might be abrogated for new reasons, or their observance might be dispensed with in regard to particular persons, by special privilege; but since, in their enactment, the perpetual decency of nature was alone regarded, not even a dispensation of them would be permissible. It may indeed be decreed that it should be lawful and unpunished, since it is in the power of princes to remit penalties; yet no legislator can effect that a thing, which nature pronounces to be vicious, should not be vicious; and, if tyrannical arrogance dares to attempt it, the light of nature will presently shine forth and prevail. When, formerly, the Emperor Claudius had married his niece Agrippina, (89) for the purpose of averting the shame, he procured a Senatusconsultum, which licensed such marriages; yet no one was found to imitate his example, except one freedman. Hence, just and reasonable men will acknowledge that, even amongst heathen nations, this Law was accounted indissoluble, as if implanted and engraved on the hearts of men. On this ground Paul, more severely to reprove the incest of a step-son with his father’s wife, says, that such an occurrence “is not so much as named among the Gentiles.” (1 Corinthians 5:1.)

If it be objected that such marriages are not prohibited to us in the New Testament, I reply, that the marriage of a father with his daughter is not forbidden; nor is a mother prohibited from marrying her son; and shall it therefore be lawful for those, who are near of kin, to form promiscuous connections? (90) Although Paul expressly mentions only one kind of incest, yet he establishes its disgrace by adducing the example of the Gentiles, that at least we should be ashamed if more delicacy and chastity is seen amongst them. And:. in fact, another admonition of the same Paul is enough for me, who thus writes to the Philippians:

“Whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.” (Philippians 4:8.)

As to those who ascend or descend ill a direct line, it, sufficiently appears that there is a monstrous indecency in the connection of father and daughter, or mother and son. A licentious poet, (91) being about to relate the frantic incest of Myrrha, says:

Daughters and fathers, from my song retire,
I sing of horror.”

In the collateral line, the uncles on both sides represent the father, and the aunts the mother; and, consequently, connection with them is forbidden, inasmuch as it would be of somewhat similar impropriety. The same rule affects affinity; for the step-mother, or mother-in-law, is held to stand in the relation of mother; and the step-daughter, or daughter-in-law, in that of daughter; as also the wife of the paternal or maternal uncle is to be regarded in the relation of mother. And, although express mention may not be made of it here, we must form our judgment by analogy as to what is prohibited; — the uncle on the father’s or mother’s side is not here forbidden to marry his niece; but, since the nephew is interdicted from marrying his paternal or maternal aunt, the mutual relation of the inferior to the superior degree must prevail. But if any should contend that there is a difference, the reason added by Moses refutes his objection, for it is said, “She is thy father’s or thy mother’s near kinswoman.” Hence it follows, that a niece is guilty of incest if she marries her uncle on either side. As to brothers and sisters, God pronounces that marriage with a sister, although she be not uterine, is unlawful; for He forbids the uncovering of the turpitude of a sister, who is either the daughter of thy father or thy mother.

“Dira canam: procul hinc natae, procul este parentes.”