8 Byzantine in culture, the brothers Cyril and Methodius succeeded in becoming apostles of the Slavs in the full sense of the word. Separation from one's homeland, which God sometimes requires of those he has chosen, when accepted with faith in his promise is always a mysterious and fertile pre-condition for the development and growth of the People of God on earth. The Lord said to Abraham: "Go from your country and your kindred and your father's house to the land that I will show you. And I will make of you a great nation, and I will bless you, and make your name great, so that you will be a blessing". In the dream which Saint Paul had at Troas in Asia Minor, a Macedonian, therefore an inhabitant of the European continent, came before him and implored him to come to his country to proclaim there the Word of God: "Come over to Macedonia and help us. Divine Providence, which for the two holy Brothers expressed itself through the voice and authority of the Emperor of Byzantium and of the Patriarch of the Church of Constantinople, addressed to them a similar exhortation, when it asked them to go as missionaries among the Slavs. For them, this task meant giving up not only a position of honour but also the contemplative life. It meant leaving the area of the Byzantine Empire and undertaking a long pilgrimage in the service of the Gospel among peoples that, in many aspects, were still very alien to the system of civil society based on the advanced organization of the State and the refined culture of Byzantium, imbued with Christian principles. A similar request has addressed three times to Methodius by the Roman Pontiff, when he sent him as Bishop among the Slavs of Greater Moravia, in the ecclesiastical regions of the ancient Diocese of Pannonia.
Source: Slavorum Apostoli (Vatican.va)