Diocese of Allentown celebrated the feast day of Pope St. Leo the Great, one of the Catholic Church’s 36 Doctors of the Church.

The feast day was observed Wednesday with a prayer the diocese posted to its Facebook page: "Saint Leo, Pope and Doctor of the Church, you were the Church's instrument in strengthening the teaching of true doctrine. Righteous Leo, entreat Christ God to grant us His great mercy."

Pope St. Leo the Great was elected to the papacy in 440 A.D., and, according to the Franciscan Media website, "displayed endless dedication as Pope."

His pastoral care of his congregants resulted in enduring sermons; one is still is used in the Office of Readings on Christmas, according to the group's website. During his papacy, Pope St. Leo fought heresies such as Pelagianism (the assertion people can rely on free will, not God, to lead a moral life, as defined by Brittanica); and Manichaeism (described by New Advent as a rejection of divine mystery and assertion that reason can explain unknowns).

Pope St. Leo is also recognized for clarifying a number of doctrinal controversies and even defending Rome from attack in his role of peacemaker, according to Franciscan Media. But it was his dedication his flock that lead to his sainthood: "His growth to sainthood has its basis in the spiritual depth with which he approached the pastoral care of his people," the website states. 

The title Doctor of the Church is designated by the Pope "in recognition of the outstanding contribution a person has made to the understanding and interpretation of the sacred Scriptures and the development of Christian doctrine," according to the Crossroads Initiative. Only 36 individuals have been given this title throughout history.