Eusebius of Caesarea

A great struggle befals men in their ascent to heaven. For that men clothed with mortal flesh should be able to subdue pleasure and every unlawful appetite, desiring to imitate the life of angels, must be compassed with violence. But who that looking upon those who labour earnestly in the service of God, and almost put to death their flesh, will not in reality confess that they do violence to the kingdom of heaven.