Halakhah к Мишлей 22:4

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 - that 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 had himself precede any priest, because of his wisdom - 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).