Where Did the Christianity in Beowulf Come From?
The Christian influences in Beowulf ultimately came from the Christian/Catholic Church of Rome which converted Romans, and thereby the Roman legions and thereby the occupied provinces. Also the Christian/Catholic Bishop of Rome sent missionary priests and monks to the British Isles to proselytze the population. There are additional considerations too.
First of all, let us be clear about the fact that the conversion of Britain to Christianity began quite early. The Catholic priest Venerable Bede, born in Bernicia, Northumbria, around 673, states in Bk 1, Ch 4 of his Ecclesiastical History of the English People that while Eleutherius was Bishop of Rome (175-189AD), a king of Britain named Lucius requested of the Pope that the king be baptized a Catholic by papal decree:
In the year of our Lord 156 Marcus Antoninus Verus was made emperor together with his brother Aurelius Commodus. He was the fourteenth after Augustus. In their time, while a holy man called Eleutherius was bishop of the church at Rome, Lucius, a king of Britain, sent him a letter praying him that he might be made a Christian by a rescript from him. His pious request was quickly granted and the Britons preserved the faith which they had received, inviolate and entire, in peace and quiet, until the time of the Emperor Diocletian.
Bede’s last sentence in the passage implies that Christianity had already been established in Britain for some time prior to Eleutherius occupying Peter’s chair from 175-189. This seems reasonable according to what is written by the historian Eusebius Pamphilus, bishop of Caesarea, in His Ecclesiastical History written in the 300’s. The Ecclesiastical History is a history of the primitive church from the time of the apostles until the 300’s when Eusebius died. Eusebius quotes the then-existent works of earlier writers like the Jewish historian Josephus, the philosopher Philo, Clement, Papias, and church writers like Dionysius of Corinth and Caius who lived before the year 100. In Book2, chapter14 of the Ecclesiastical History Eusebius recounts how the anti-Christian Simon Magus encountered Peter the apostle in Rome:
He [Simon Magus] undertook a great journey from the East across the sea and fled to the West, thinking that this was the only way for him to live according to his mind. Entering the city of Rome, by the cooperation of that malignant spirit which had fixed its seat there, his attempts were soon so far successful as to be honored as a god with the erection of a statue by the inhabitants of that city. This, however, did not continue long; immediately under the reign of Claudius, by the benign and gracious providence of God, Peter, that powerful and great apostle, who by his courage took the lead of all the rest, was conducted to Rome against this pest of mankind. He, like a noble commander of God fortified with the divine armor, bore the precious...