The Holy Equal-to-the-Apostles first teachers and enlighteners of the Slavs, the brothers Cyril and Methodius, came from a noble and pious family living in the Greek city of Thessalonica. Saint Methodius was the eldest of the seven brothers, Saint Constantine (Cyril was his monastic name) was the youngest. Saint Methodius was at first in the military rank and was the ruler of one of the Slavic principalities subordinate to the Byzantine Empire, apparently Bulgarian, which gave him the opportunity to learn the Slavic language. 
After staying there for about 10 years, Saint Methodius then became a monk in one of the monasteries on Mount Olympus. Saint Constantine was distinguished by great abilities from an early age and studied with the young Emperor Michael with the best teachers in Constantinople, including Photius, the future Patriarch of Constantinople. Saint Constantine perfectly comprehended all the sciences of his time and many languages, and he studied the works of Saint Gregory the Theologian especially diligently. For his intelligence and outstanding knowledge, St. Constantine received the nickname of the Philosopher (the Wise). After completing his studies, Saint Constantine became a priest and was appointed curator of the patriarchal library at St. Sophia's Church, but soon left the capital and secretly entered a monastery. Found there and returned to Constantinople, he was appointed a philosophy teacher at the Higher School of Constantinople. The wisdom and strength of faith of the still very young Constantine were so great that he managed to defeat the leader of the iconoclastic heretics Annius in the debate. After this victory, Constantine was sent by the emperor to debate about the Holy Trinity with the Saracens (Muslims) and also won. Returning, Saint Constantine retired to his brother Saint Methodius on Olympus, spending his time in unceasing prayer and reading the works of the holy fathers.
Soon the emperor summoned the two holy brothers from the monastery and sent them to the Khazars to preach the gospel. On the way, they stopped for a while in the town of Korsun, preparing for the sermon. There, the holy brothers miraculously found the relics of the Holy Martyr Clement, Pope of Rome (commemorated on November 25). Russian Russian-speaking Saint Constantine found a Gospel and a Psalter written in "Russian letters" and a man in Korsun, and he began to learn from this man to read and speak his language. After that, the holy brothers went to the Khazars, where they won the debate with Jews and Muslims, preaching the gospel teaching. On their way home, the brothers visited Korsun again and, taking the relics of St. Clement there, returned to Constantinople. Saint Constantine remained in the capital, and Saint Methodius received the abbacy in the small monastery of Polychron, near Mount Olympus, where he had previously labored.
Soon, ambassadors from the Moravian prince Rostislav, who was oppressed by the German bishops, came to the emperor with a request to send teachers to Moravia who could preach in the Slavs' native language. The emperor called Saint Constantine and told him, "You must go there, for no one can do it better than you." Saint Constantine began a new feat with fasting and prayer. With the help of his brother Saint Methodius and his disciples Gorazd, Kliment, Savva, Nahum and Angelyar, he compiled the Slavic alphabet and translated into Slavic the books without which Worship could not take place: the Gospel, the Apostle, the Psalter and selected services. It was in the year 863.
After completing the translation, the holy brothers went to Moravia, where they were received with great honor and began to teach worship in the Slavic language. This provoked the anger of the German bishops, who celebrated services in Latin in the Moravian churches, and they rebelled against the holy brothers, arguing that worship could only be performed in one of three languages: Hebrew, Greek or Latin. Saint Constantine replied to them: "You recognize only three languages worthy of praising God in them. But David is crying out: "Sing to the Lord, all the earth, praise the Lord, all the nations, let every breath praise the Lord!" And the Holy Gospel says, "Go and teach all tongues...." The German bishops were put to shame, but they became even more embittered and filed a complaint with Rome. The Holy brothers were called to Rome to resolve this issue. Taking with them the relics of St. Clement, the pope, Saints Constantine and Methodius set off for Rome. Having learned that the holy brothers were carrying holy relics with them, Pope Adrian and the clergy went out to meet them. The Holy brothers were greeted with honor, the Pope approved divine services in the Slavic language, and ordered the books translated by the brothers to be placed in Roman churches and the liturgy celebrated in the Slavic language.
While in Rome, Saint Constantine fell ill and, informed by the Lord in a miraculous vision of his approaching death, accepted the schema with the name Cyril. 50 days after the adoption of the schema, on February 14, 869, Equal-to-the-Apostles Cyril died at the age of 42. Departing to God, Saint Cyril commanded his brother, Saint Methodius, to continue their common cause – the enlightenment of the Slavic peoples by the light of the true faith. Saint Methodius begged the pope to allow his brother's body to be taken away for burial in his native land, but the pope ordered the relics of Saint Cyril to be placed in the church of Saint Clement, where miracles began to be performed from them.
After the death of Saint Cyril, the pope, following the request of the Slavic Prince Kotsel, sent Saint Methodius to Pannonia, ordaining him Archbishop of Moravia and Pannonia, to the ancient see of Saint Andronikos the Apostle. In Pannonia, Saint Methodius, together with his disciples, continued to spread worship, writing, and books in the Slavic language. This again provoked the fury of the German bishops. They secured the arrest and trial of St. Methodius, who was exiled to Swabia, where he suffered many sufferings for two and a half years. Released by order of Pope John VIII and reinstated as archbishop, Methodius continued evangelical preaching among the Slavs and baptized Czech Prince Borivoy and his wife Lyudmila (September 16), as well as one of the Polish princes. For the third time, German bishops began to persecute the saint for not accepting the Roman doctrine of the descent of the Holy Spirit from the Father and from the Son. Saint Methodius was summoned to Rome, but justified himself before the pope, preserving the purity of Orthodox teaching, and was again returned to the capital of Moravia, Velegrad.
Here, in the last years of his life, Saint Methodius, with the help of two priestly students, translated the entire Old Testament into Slavic, except for the Maccabean books, as well as the Nomocanon (Rules of the Holy Fathers) and patristic books (Patericus).
Sensing the approach of his death, Saint Methodius pointed to one of his disciples, Gorazd, as a worthy successor. The saint predicted the day of his death and died on April 6, 885, at the age of about 60. The funeral service of the saint was performed in three languages – Slavic, Greek and Latin; he was buried in the cathedral church of Velegrad.