Ambrose of Milan

But what does this signify, that after Aaron was dead, the Lord commanded, not the whole people, but Moses alone, who is amongst the priests, to clothe Aaron's son Eleazar with the priest's garments, except that we should understand that priest must consecrate priest, and himself clothe him with the vestments, that is, with priestly virtues; and then, if he has seen that nothing is wanting to him of the priestly garments, and that all things are perfect, should admit him to the sacred altars. …

Epistle 63 ↗