Part of my morning exercises over the last year is reading through Cyril of Alexandria’s commentary on John (not that I always get to it daily). Cyril, like most other Early Church Fathers, was quick to speak about eternal punishment. In his commentary on John 8:21, “I am going away, and you will seek me, and you will die in your sin,” Cyril notes that Jesus is speaking warning here in order to graciously turn people away from hell.
For to die unredeemed, yet laden with the weight of sin, to whom is it any doubt where this will conduct the soul of man? For deep Hades will, I deem, receive such an one, and he will continue in great darkness, yea he will inhabit fire and flames, with reason numbered among those of whom it has been said by Prophet’s voice, Their worm shall not die neither shall their fire be quenched, and they shall be for a sight to all flesh. Whereof that they may escape the trial, Christ kept manifoldly calling them to a speedy turning away from their wonted unbelief, saying not only that He should leave them and go away, but also of necessity putting before them how great misfortune they will thence undergo.Cyril of Alexandria, Commentary on the Gospel according to S. John, vol. 1 (Oxford; London: James Parker & Co.; Rivingtons, 1874), 580.