Leviticus 18:6-19 and 20:17-21 are duplicate lists of all prohibited heterosexual relationships, and all of them detail sexual prohibitions between a variety of different family members. These sexual prohibitions are furthermore encased by priestly exhortations to be holy. “You shall make yourselves holy and you shall be holy, because I am Yahweh your god’ (Lev 20:7).
Thus, the list of sexual prohibitions is used to separate out those impure and unholy sexual unions. They are even invoked in the terms of sacred violations: you shall not “expose the nudity” of so-and-so. Not only does the Priestly writer label these sexual unions as a perversion, impurity, and an aberration, but he stresses that any man engaged in such unholy acts “shall be cut off from among the people.” It would seem that there is no atoning for such violations. The guilty person is excommunicated from both Yahweh’s people and his land (cf. #190).
The last sexual prohibition in chapter 20 is for a man who exposes his brother’s nudity.
“And a man who will take his brother’s wife: it is an impurity He has exposed his brother’s nudity. They will be childless.” (Lev 20:21)
The crime cannot denote adultery, since that has been treated earlier (#192), and is a much more severe violation. Rather the Priestly writer is directly refuting an earlier tradition that was preserved in Deuteronomy—namely, that in cases where a wife’s husband has died and there was no son, the dead man’s brother, the brother-in-law, may step in and marry his brother’s wife and bear seed for him (Deut 25:5). In fact, in the Deuteronomic tradition the brother-in-law is obliged to step in and marry his brother’s wife.
The Priestly legislation makes no exceptions; a brother-in-law cannot marry is brother’s wife. In fact it is more likely that P wrote to refute the earlier Deuteronomic code.
Again the differences between the Priestly writer’s condemnation of such acts, legitimated through the mouthpiece of his god Yahweh, and the Deuteronomist’s position, which is also expressed through the mouthpiece of Moses, and acknowledged as having been received by Yahweh at Horeb—that is a mere week before Yahweh recants the law in the now combined PD narrative!—are indicative of larger theological and religious differences between these two priestly rivals (see for example #152, #153-154, #172, #177, #178, etc.).
The Priestly writer’s focus was ritual, ritual purity, and maintaining that purity or holiness. The Deuteronomist’s brand of religion was secular rather than cultic or ritualistic. Its focus was on secular issues. So in the present case, having a brother-in-law come in and do the duty of a dead brother was only natural; such laws were meant to contribute to a more humanitarian or secularized society.
For the ritually focused Priestly writer the very act of a brother-in-law marrying his brother’s wife would have not only been unnatural but more so would have been seen as an act that defiled the dead brother and breached the conducts of purity as commanded by Yahweh, according to this author. To visualize this in the manner that the Priestly writer suggests: any man marrying his brother’s wife has just exposed his own brother’s genitalia! And this is a no no. The befitting punishment is childlessness and being cut off. The very fact that the punishment is that they should go childless clearly reveals that the Priestly writer, through the mouthpiece of Yahweh, was directly refuting the position of the Deuteronomist.
Recall that in the Deuteronomic law code, a brother-in-law marries his brother’s wife for the sole purpose of raising up his offspring! Thus against the Deuteronomist’s Mosaic law that requires a brother-in-law to step in and produce offspring for his late brother wife, the Priestly writer lashes back with a stern polemic—if a brother-in-law were to do such a thing, they will both be barren and excommunicated.
As noted previously, studying the Bible objectively reveals that such law codes were written by different elite guilds, and they reflect their differing beliefs, values, and worldviews. Such differences were then legitimated and authorized by placing them on the lips of this culture’s deity, Yahweh. But in fact, we see that both Yahweh and his laws were created and shaped by the pen of these elite scribes.