We have already seen in contradiction #91 how the later Priestly writer modified the tradition that he inherited so that it better suited his own ideology and legitimated his own priestly guild, while on the other hand denigrated that of the Levites, whose forefather was Moses.
Yet nowhere is the Priestly writer’s bias against Moses more pronounced than in his rewriting of E’s Moses, who is literally “heavy of mouth and tongue” (Ex 4:10), to “uncircumcised of lips” (Ex 6:12). Again, these were literary techniques employed by biblical scribes as a means to polemically denigrate the claims of a rival priesthood, here the Levites, by portraying their founding figure in defamatory and unflattering terms. P’s choice of words presents a Moses who is now equated with ritual defilement!
Ezekiel, for example, who was an Aaronid priest himself, labeled this as a disqualification from the priesthood (Ezek 44:7-9). Thus the Priestly writer, in rewriting the E tradition, uses this as yet another occasion to promulgate his particular pro-Aaronid, anti-Mushite propaganda: Moses and those Levites tracing their ancestry back to Moses are unqualified for the priesthood. We will see later on that the Priestly writer makes this explicit in a number of places, demoting the Levites to mere servants of the Aaronid priesthood!
On a broader level, here is what the Priestly writer has done in retelling the Moses story. In the reconstructed P document (which you can visually see in Friedman’s The Bible with Sources Revealed), there is no personal history for Moses; he never travels to Midian, never encounters Yahweh in a bush. Moses seems to have no wife, and certainly not a Midianite wife, and no children in P. The snake/serpent trick (#92) is not performed by Moses in P, but by Aaron, and with Aaron’s rod. And P makes Aaron Moses’ older brother not just his Levite brethren as in E.
The whole re-written Priestly narrative is an attempt to downplay the importance of Moses while highlighting Aaron as the central and most significant figure. We will revisit this in later contradictions in both Exodus and Leviticus. We will also have the occasion to see how this legitimization extends itself to even having Yahweh demote the Levites and justify the Aaronids as his sole officiating priests, as well as legitimate their core theological and cultic laws. This is all part of what ancient literature does and how it was used.