Grande Munus §10

¹⁰ After these things had taken place, Methodius returned under Papal orders to Moravia as bishop. In that province, having become a spiritual model for his flock, he began to serve Catholicism more keenly every day. He strongly resisted the factions of reform, lest the Catholic name fall through unsound thinking. He educated prince Svatopluk, who succeeded Rastislav in religious matters. He warned him about shirking his duties, rebuked him, and finally excommunicated him. For these reasons he incurred the anger of that revolting and wicked tyrant; then he was sent into exile. He was recalled a short time later, and his efforts produced a change of heart in the prince and an understanding that he should return to a new purity of life.