The prohibitions of various sexual relationships, enumerated in the book of Leviticus and included in the most recent Sabbath Torah reading, are prefaced by a command not to imitate the ways of the Egyptians or the Canaanites, and are followed by another admonition not to imitate Canaanite practices. The text thereby seems to suggest that such relationships, most of which involve forms of incest, were commonplace among both peoples. While little is known about Canaanite law and marital practices, Eve Levavi Feinstein draws upon Hammurabi’s Code (18th century BCE), a Hittite legal code (ca. 1650–1500 BCE), and Egyptian documents to place the biblical prohibitions in context:
The sexual prohibitions in the laws of Hammurabi and the Hittite laws have some affinities with those in Leviticus but are significantly less restrictive. Later Hittite law and [a 14th-century-BCE] treaty point to a wider range of restrictions, but the latter intimates that they were not the norm throughout the region. While the data are limited, these texts at least suggest that the laws of Leviticus 18 were not simply a reflection of the norms prevailing throughout the ancient Near East. They were distinct and most likely unusually strict. . . .
Although Egypt certainly forbade adultery, incest does not seem to have been an Egyptian taboo. As early as the 14th century BCE and through at least the Ptolemaic period [the 3rd and 2nd centuries BCE], some Pharaohs married their half or full sisters. There are also documented cases of non-royal marriages between children of the same father from the Middle Kingdom (ca. 1975-1640 BCE) and the Twenty-Second Dynasty (ca. 945-715 BCE), including some that appear to involve full siblings, as well as one marriage between a father and daughter.
The most extensive information on this subject comes from an official census from the 2nd century CE. In the most comprehensively documented region covered by the census, the district capital of Arsinoe, southwest of modern Cairo, 37 percent of all documented marriages are between full siblings.
Taking into account that not everyone has an available opposite-sex sibling and that there was a strong preference for younger women to marry older men, this is close to the maximum of possible sibling marriages. It is the highest level of inbreeding of any known population. Combined with the earlier material, it suggests that Egypt had a very long history of accepting and even favoring marriage between close kin, especially siblings.