Pope St. Anastasius I (4th century)
Anastasius, a friend of St. Augustine, St. Jerome, and St. Paulinus, was known for his condemnation of the heretical writings of Origen. He convened a synod to condemn his works. He also fought the heresy of Donatism.

Reflections from the Saints

Occupy your minds with good thoughts, or the enemy will fill them with bad ones. Unoccupied, they cannot be.
– St. Thomas More