Although what I have recorded did not occur to Athanasius and the church of Alexandria, at the same period of time after the death of Constans, yet I deemed it right, for the sake of greater clearness, to relate all these events collectively. The council of Milan was dissolved without any business having been transacted, and the emperor condemned to banishment all those who had opposed the designs of the enemies of Athanasius. As Constantius wished to establish uniformity of doctrine throughout the Church, and to unite the priesthood in the maintenance of the same sentiments, he formed a plan to convene the bishops of every religion to a council, to be held in the West. He was aware of the difficulty of carrying this scheme into execution, arising from the vast extent of land and seas which some of the bishops would have to traverse, yet he did not altogether despair of success. While this project was occupying his mind, and before he prepared to make his triumphal entrance into Rome, he sent for Liberius, the bishop of Rome, and strove to persuade him to conformity of sentiment with the priests by whom he was attended, amongst whom was Eudoxius. As Liberius, however, refused compliance, and protested that he would never yield on this point, the emperor banished him to Beroea, in Thrace. It is alleged, that another pretext for the banishment of Liberius was, that he would not withdraw from communion with Athanasius, but manfully opposed the emperor, who insisted that Athanasius had injured the Church, had occasioned the death of the elder of his two brothers,
Christianity · Church History · Ecclesiastical History
Book IV, Ch. 11 — Liberius, Bishop of Rome, and the cause of his being exiled by Constantius. Felix his Successor.
Ecclesiastical History · Salminius Hermias Sozomen