6 None of you shall approach to any that is near of kin to him, to uncover their nakedness: I am the Lord. 

7 The nakedness of thy father, or the nakedness of thy mother, shalt thou not uncover: she is thy mother; thou shalt not uncover her nakedness. 

8 The nakedness of thy father’s wife shalt thou not uncover: it is thy father’s nakedness. 

9 The nakedness of thy sister, the daughter of thy father, or daughter of thy mother, whether she be born at home, or born abroad, even their nakedness thou shalt not uncover. 

10 The nakedness of thy son’s daughter, or of thy daughter’s daughter, even their nakedness thou shalt not uncover: for theirs is thine own nakedness. 

11 The nakedness of thy father’s wife’s daughter, begotten of thy father, she is thy sister, thou shalt not uncover her nakedness.

The first batch of forbidden behavior is incestuous relationships. Today covers the nearest of kin: parents, siblings, grandchildren, and stepsiblings, and then over the next couple days we will expand to more distant relationships, such as uncles and aunts. God will set the minimum number of degrees of separation there must be between a couple in Israel.

Interestingly, Abraham’s marriage to Sarah would not have met the standard required in these verses. Sarah, we learn, was the daughter of his father, but not of his mother. She was his stepsister. Obviously, there must have been a time where Adam and Eve’s children were coupling with one another, and while the population grew, closely related pairings were likely still common. One should not view these early-population examples as a contradiction to the law here described. Humanity had not yet fully come into its own, like a still-developing child. Once the species was mature, God established the rules that would thereafter govern it, and that included the prohibitions on near relationships, and we should look for no more exceptions to it.