Sefer HaChinuch ספר החינוך

The commandment of sanctifying the seed of Aharon: To sanctify the seed of Aharon, meaning to say, to sanctify them and to bring them in to the sacrifice, and that is the essence of the positive commandment — and likewise to have them precede in every thing of holiness. And if they refuse this, we do not listen to them. And this is all for the honor of God, may He be elevated, since He took them and chose them for His service. As it is stated (Leviticus 21:8), “And you shall make him holy” — for every thing in holiness: to open first; to bless first; and to take a nice piece first. And the language of Sifra, Emor, Chapter 1:13 is “‘And you shall make him holy,’ against his will” — meaning to say that we are commanded in this commandment and it is not the choice of the priest. And they also said (Sifra, Emor, Chapter 1:13), “‘Holy shall they be to their God’ (Leviticus 21:6) — against their will; ‘and they will be holy’ — to include those with blemishes, that we not say, ‘Since those are not fitting “to offer the bread of their Lord,” why should we have this one precede and we honor him?’ Hence, its stating, ‘and they will be holy’” — meaning that all of the seed is holy, [both] those unblemished and those with blemishes.

It is from the roots of the commandment [that it is] since it is known that honoring his servants is from the honor of the master. And every time we honor the priests, we remember and fix His honor, blessed be He, and His greatness in our thoughts. And in the merit of this pure thought and loftiness and good will, His blessing and His great goodness will descend upon us. And He desires blessing, as we have informed several times.

From the laws of the commandment is that which they said (Gittin 39a) that the order of the communal reading of the Torah is like this: the priest (Kohen) always reads first; and a Levite after him; and an Israelite after him. But if there is no priest there, the package is undone. And if there is no Levite, a priest reads twice. But a priest does not read after a priest, because of [the appearance of] the defect of the first. And a Levite does not read after a Levite, because of [the appearance of] the defect of both of them. And this honor is done for them if they are fitting it. But if they are sinners, we prevent them from honor. And they, may their memory be blessed, already said (Horayot 13a) that a mamzer Torah scholar precedes an ignoramus high priest. But today at this time, we have not seen [anyone] who, because of his wisdom, had himself precede any priest — and “following modesty is the fear of the Lord.” And the rest of its details are elucidated in scattered places of the Gemara: Makkot; Chullin; Bekhorot; Shabbat; and the rest of them. (See Mishneh Torah, Laws of Vessels of the Sanctuary and Those Who Serve Therein 8.)

And [it] is practiced in every place and at all times by males and females, as it is a commandment upon all of them to honor the seed of Aharon. And one who transgresses it and does not honor them in a place that is fitting and [with] a priest that is fitting to honor has violated this positive commandment.