Bede — on Rev 8:8 (Commentary on Revelation)

“And as it were a great mountain burning with fire, was cast into the sea, etc. With the growth of the Christian religion, the devil, swollen with pride and burning with the fire of his fury, was cast into the sea of the world, with the Lord saying: "If you say to this mountain, be taken up and cast into the sea, it will be done" (Mark 11). Not that he was not there before, but that, having been cast out from the Church, he began to rage more greatly against his own, inflicting spiritual death on them with the pride of carnal wisdom. For to think according to the flesh is death (Romans 8). But the apostles were not taught by flesh and blood, but by the Father who is in heaven (Matthew 16). For in that sea, they steered the ship of faith which offered itself to be trodden by the feet of the Lord.”