This Sabbath, Jewish congregations begin reading the third book of the Bible, which is concerned almost exclusively with ritual matters: sacrifices, purity and impurity, dietary restrictions, and the like. Many of these laws apply exclusively to the kohanim—the members of the priestly caste made up of descendants of Aaron—rather than to the Israelites as a whole. So why, asks Jeffrey Tigay, include them all in the Torah?
One clue seems to be found in Leviticus 21, a chapter that is addressed [explicitly] to the priests: “And the Lord said to Moses: ‘Speak to the priests, the sons of Aaron, and say to them . . .’”. The chapter requires the priests to avoid actions . . . that would disqualify them from officiating. Surprisingly, the final verse of the chapter . . . adds that it was addressed to the people as well: “Thus Moses spoke to Aaron and his sons and to all the Israelites.” . . .
Moses seems to be informing the people of the rules incumbent on priests in order to [enable] the people to make sure that the priests comply. This enables us to view this chapter, and all the priestly laws, in the larger context of the Torah’s instructions to make all of its laws public.
Making the laws public informs the people not only of their own duties but also of the duties of public officials (priests and prophets, judges and kings), including the limits that God placed on the officials’ rights. [It thus makes possible] public scrutiny and criticism of officials and prevents them from gaining the absolute authority and prestige that they would command by controlling important information known only to them. . . .
[In ancient times], teaching the laws to the entire citizenry was unusual. . . . This aspect of biblical religion was expressed artistically in the frescoes from the 3rd century CE discovered in the ancient Syrian city of Dura Europos. As [the great historian of ancient Judaism] Elias Bickerman wrote, “The sacred books of all other religions . . . were ritual texts to be used or recited by priests. In the temple of Mithras at Dura it is a Magian in his sacred dress who keeps the sacred scroll closed in his hand. [But] in the synagogue of Dura, a layman, without any sign of office, is represented reading the open scroll.”
Read more on theTorah.com: https://thetorah.com/why-are-laws-for-priests-included-in-the-torah/