The Instructions of Commodianus 67

Exercise the mystery of Christ, O deacons, with purity; therefore, O ministers, do the commands of your Master; do not play the person of a righteous judge; strengthen your office by all things, as learned men, looking upwards, always devoted to the Supreme God. Render the faithful sacred ministries of the altar to God, prepared in divine matters to set an example; yourselves incline your head to the pastors, so shall it come to pass that ye may be approved of Christ.