Incest in the Bible refers to sexual relations between certain close kinship relationships which are prohibited by the Hebrew Bible. These prohibitions are found predominantly in and , but also in Deuteronomy. Jewish views on incest are based on the biblical categories of forbidden relationships and have been subject to rabbinic interpretations in the Talmud. (See also Forbidden relationships in Judaism.) The Karaites reject the authority of Talmudic opinions and interpret the biblical prohibitions differently. The various Christian denominations set their own categories of prohibited incestuous relationships, which have changed from time to time. (See Affinity (Catholic canon law).) The laws of many countries regarding prohibited relationships do not necessarily follow the biblical prohibitions nor those of any particular church. (See Legality of incest.)
In ancient times, tribal nations preferred endogamous marriage marriage to one's relatives; the ideal marriage was usually that to a cousin, and it was often forbidden for an eldest daughter to even marry outside the family. Marriage to a half-sister, for example, is considered incest by most nations today, but was common behaviour for Egyptian pharaohs; similarly, the Book of Genesis portrays Sarah as marrying Abraham, her half-brother, without criticising the close genetic relationship between them, and the Book of Samuel treats the marriage of a royal prince to his half-sister as unusual, rather than wicked.
Prohibited relationships
and sets out lists of prohibited relationships, and two chapters later specifies punishments for such unions, but the second list of unions is much shorter than the first. Critical scholars regard the lists as having originally been independent documents, bound together at a later point. The Deuteronomic Code gives a yet more simple list of prohibited relationships a man's parent's daughter (including his sister), a man's father's wife (including his mother), and a man's mother-in-law. In the Hebrew Bible, sexual relationships between siblings are forbidden to Jews but permissible to Gentiles (non-Jews).
The relationships prohibited by Leviticus 18 are:
One's mother () One's father () One's stepmother () One's paternal or maternal sister () One's paternal sister through one's father's wife () One's daughter (inferred from ) One's granddaughter () A woman and her daughter () A woman and her granddaughter () One's aunt by blood () One's father's brother (uncle) () One's father's brother's wife (aunt) () One's daughter-in-law () One's brother's wife (sister-in-law) (), with the exception of Yibum One's wife's sister (sister-in-law) during one's wife's lifetime, even if since divorced ()
The lists of prohibited relationships can be summarised as follows (the relations highlighted in red are those that are prohibited):
One of the most notable features of each list is that sexual relations between a man and his own daughter is not explicitly prohibited. Although the first relation mentioned after the Levitical prohibition of sex with "near kin" names that of "thy father", it must be taken into account that the Hebrew original text only addresses male Jews with regard to their female relatives. The Talmud argues that the absence is because the prohibition was obvious, especially given the proscription against a relationship with a granddaughter, although some biblical scholars have instead proposed that it was originally in the list, but was then accidentally left out from the copy on which modern versions of the text ultimately depend, due to a mistake by the scribe. The second list in the Holiness code noticeably differs from the first by not including the closer relatives, and it might be assumed that obviousness is the explanation here as well. One might argue that the explicit prohibition against engaging in sexual activity with a woman as well as with her daughter, implicitly forbids sexual activity between a man and his daughter. However, the rationale might suggest otherwise (the original text is unclear here), since it mentions only that "they" (i.e., the woman and the daughter) are related. John Calvin did not consider the father-daughter-relation to be explicitly forbidden by the Bible, but regarded it as immoral nevertheless.
Apart from the case of the daughter, the first incest list in Leviticus roughly produces the same rules as applied in early (pre-Islamic) Arabic culture; in Islam, these pre-Islamic rules were made statutory.