The Work of Ulfilas among the Goths(Philostorgius) says that at this time Ulfilas led a large body of the Scythians (Goths) from those living across the Ister (the people whom in olden times they called Getae, but now call Goths) to the land of the Romans, driven through piety from their own homes. Now this people became Christian in the following way. In the reigns of Valerian and Gallienus (253-268), a large number of Scythians from beyond the Ister (Danube) crossed into Roman territory and overran much of Europe. Crossing also into Asia, they reached as far as Galatia and Cappadocia. They took many prisoners, including some who were members of the clergy, and went home with a great quantity of booty. Now the pious band of prisoners, living as they did among the barbarians, converted many of them to the way of piety and persuaded them to adopt the Christian faith instead of the pagan. Among these prisoners were the ancestors of Ulfilas; they were Cappadocians by nationality, from a village near the city of Parnassus called Sadagolthina.
It was this Ulfilas who led the exodus of the pious ones, being the first bishop appointed among them. He was appointed in the following circumstances: sent with others by the ruler of the race of the Goths on an embassy in the time of Constantine [probably a mistake for Constantius II, 337-361] -- for the barbarian peoples in those parts owed allegiance to the emperor, Ulfilas was elected by Eusebius (of Nicomedia) and the bishops of his party (the Arians) as bishop of the Christians in the Getic land. Among the matters which he attended to among them, he was the inventor for them of their own letters, and translated all the Scriptures into their language - with the exception, that is, of the Books of Kings. This was because these books contain the history of wars, while the Gothic people, being lovers of war, were in need of something to restrain their passion for fighting rather than to incite them to it, which those books have the power to do, for all that they are held in the highest honour, and are well fitted to lead believers to the worship of God. The emperor established this mass of refugees in the territories of Moesia, where each man chose to live; and he held Ulfilas in the highest esteem, so as often to refer to him as the "Moses of our time." Philostorgius admires this man to excess, and records that with those in his charge he was attached to the same heretical opinions as himself.
Philostorgius Ecclesiastical History 2. 5, as excerpted by Photius