Leviticus 18:6 - Matthew Poole's English Annotations on the Holy Bible

None, Heb. no man, For though the women also be bound by this law, yet the men alone are mentioned, both because they are most active in the choice of their yoke-fellows, and therefore most likely to transgress these laws, and because they having authority over the women, could have the greater influence upon them, by their power, counsel, or example, to oblige them either to the observation or violation of them. Approach: this word signifies the conjugal act here, as it doth Genesis 20:4 Isaiah 8:3; but because it is ambiguous in itself, it is so limited and explained in the end of the verse. To any that is near of kin to him: this is the general rule, which is particularly expounded and applied in the following instances. And these laws are so just and reasonable, that although the barbarous nations did allow of such incestuous marriages, yet wiser and civil heathens by the mere light of nature condemned them, as may be seen in Suetonius, Tacitus, Catullus, and others. Their nakedness, i.e. their secret parts, so called to put us in mind of the fall of our first parents, whose first sense and shame of their nakedness had its rise from thence. This phrase notes the same thing with knowing, Genesis 4:1; and with discovering one's skirt, Deuteronomy 22:30, Deuteronomy 27:20.