From the Introduction to Book XXI of - Augustine's The City of God
“The only one named by Augustine as a representative of the tender-hearted is Origen. Origen had gone so far as to include the devil and his angels among those who would eventually complete the punishment due, and be delivered from the tortures of hell (gehenna).
“Origen’s ‘hell’ is thus really a purgatory in which all sinners, whether men or angels, will finally be cleansed from their guilt and restored to peace with God . . .
“This view, along with other views of Origen, had already been condemned by the church as heretical [see footnote below], as Augustine points out. But in the meantime Origen’s doctrine had enjoyed much popularity, especially in the eastern churches. Their renowned teacher Basil himself believed in eternal punishment, but states that most ordinary Christians believed there would be a time limit. Among these, apparently, must be included his brother Gregory of Nyassa and his close friend Gregory of Nazianzus.
“Ambrose of Milan was a diligent student of the works of Origen, and though he did not adopt the notion of universal salvation, he does in one passage interpret hell metaphorically. There is no gnashing of bodily teeth, nor any perpetual fire of material flames, nor a material worm, he writes—these are mere vivid figures of the torments of a conscience which has awakened too late.” (quoted from Exposition of the Gospel of Luke, 7.205f, by Ambrose)
FOOTNOTE: “Pope Anastasius had condemned the books of Origen in the year 400. His letter to Simplicianus of Milan is preserved as No. 95 among the letters of Jerome.”