Our sages often refer to the book of Leviticus as Torat Kohanim (the Law of the Priests). Though it does contain many such laws, it is certainly not devoted exclusively to the Priests and their service.
Nonetheless, the message that “You shall be My special treasure among all the peoples… You shall be to Me a kingdom of Priests and a holy nation” (Ex. 19:5-6), which is the essence of Israel’s chosenness, appears in Leviticus with special emphasis.
The Jewish people is “a kingdom of Priests” both literally and figuratively. We are, in a sense, the Priests of all mankind, with all the obligations that derive from this calling.
The prophets, too, speak of the exceptional responsibility that goes with being chosen as “a kingdom of Priests.”
Regarding other nations, for example, God does not always make a strict accounting, whereas regarding the People of Israel it says, “You alone have I known of all the families of the earth – that is why I will call you to account for all your iniquities” (Amos 3:2).
This is not only because the greater the person, the greater his fall, and the higher his level, the lower his descent.
Rather, there is improper behavior that an ordinary person can get away with, whereas a Jew is held up to much more intense scrutiny; if he does these things, it is considered a major blemish.
This distinction can be seen in connection with prophecy.
The Talmud says that “The Holy One, Blessed Be He, causes His Divine Presence to rest only on one who is strong, wealthy, wise, and humble” (Nedarim 38a).
These qualities are required only of the prophets of Israel, and they are connected with the holiness that is unique to Israel.
In the case of all the other nations, a person who possesses none of these positive traits can still become a great prophet.
Rabbi Adin Steinsaltz