This means the individual cannot say that the priesthood does not interest him, that it is not his business and does not belong to his occupation.
A ‘holy nation’ means a whole people that is completely holy, and that is entirely destined for holiness, and each of its parts has a role to play in this framework.
However, even within the people of Israel there is a subdivision of priests who have ritual, cultic functions, of sages who teach others or strive harder in this direction.
Yet those with special roles do not exempt themselves from the rest of their duty and commitment.
The acceptance of a special role–whether it is inherited or is the result of choice or personal talent–does not free people from fulfilling their duty.
This internal hierarchy is a secondary division of roles within the general framework, and is aimed at the same objectives.
Just as the High Priest does not exempt the other priests from their priestly responsibilities, and army commanders and officers do not exempt the rest of the soldiers from their fighting duties, so those who have special duties do not exempt the others from their obligations.
For this reason there did not, and could not, exist to a formal group of religious functionaries among the people of Israel who had a status of their own.
Undoubtedly, there were, and are, such functionaries, but they do not in any way constitute a separate group because the priestly duties are the general duties of all the people.
Those who are exemplary in their service of God are simply a model for others who need to do as they do and to follow them closely.
However, the leadership that has existed for generations — the sages and their disciples — is not a closed group but one essentially aimed at and committed to continual growth.
Even if in reality there are Jews, whether few or many, who are unaware of their duties or are incapable of fulfilling them completely, their behavior is considered a deviation, an inability to do the right things, or at the most a temporary situation.
The role of priests is not one for particular individuals who are God’s servants.
This is the task of the ‘holy nation,’ the entire people, who are totally directed toward sacred matters.”
From “What Is Our Role in the World?” p. 147-149, in We Jews: Who Are We and What Should We Do? By Rabbi Adin Steinsaltz