In his epistle to the Christians of Smyrna, St. Ignatius, Martyr, says that the priesthood is the most sublime of all created dignities: “The apex of dignities is the priesthood.” St. Ephrem calls it an infinite dignity: “The priesthood is an astounding miracle, great, immense, and infinite.” St. John Chrysostom says, that though its functions are performed on earth, the priesthood should be numbered among the things of Heaven.”
According to Cassian, the priest of God is exalted above all earthly sovereignties, and above all celestial heights—–he is inferior only to God. Innocent III says that the priest is placed between God and man; inferior to God, but superior to man. St. Denis calls the priest a Divine man. Hence he has called the priesthood a Divine dignity. In fine, St. Ephrem says that the gift of the sacerdotal dignity surpasses all understanding. For us it is enough to know, that Jesus Christ has said that we should treat his priests as we would his own person: “He that heareth you, heareth Me; he that despiseth you, despiseth Me.” Hence St. John Chrysostom says, that “he who honors a priest, honors Christ, and he who insults a priest, insults Christ.” Through respect for the sacerdotal dignity, St. Mary of Oignies used to kiss the ground on which a priest had walked.
-Extracted from The Dignity of the Priest by St. Alphonsus de Liguori