Philoxenus of Mabbug

Just as with the former law of Moses, all the priests … must first offer a rational sacrifice to God for themselves, and only then for the people. In his prayer, the priest asks in the first place for forgiveness of his own sins and a cleansing of his own soul and body from all sinful thoughts and actions. Then each priest offers these prayers to God in accordance with the measure of his own purity of soul.