Nicene and Post-Nicene Fathers: Series I/Volume V/On the Merits and Forgiveness of Sins, and on the Baptism of Infants/Book I/Chapter 5

Chapter 5 [V.] —The Words, Mortale (Capable of Dying),  Mortuum (Dead), and Moriturus (Destined to Die).

Now previous to the change into the incorruptible state which is promised in the resurrection of the saints, the body could be mortal (capable of dying), although not destined to die (moriturus); just as our body in its present state can, so to speak, be capable of sickness, although not destined to be sick. For whose is the flesh which is incapable of sickness, even if from some accident it die before it ever is sick? In like manner was man&#8217;s body then mortal; and this mortality was to have been superseded by an eternal incorruption, if man had persevered in righteousness, that is to say, obedience: but even what was mortal (mortale) was not made dead (mortuum), except on account of sin. For the change which is to come in at the resurrection is, in truth, not only not to have death incidental to it, which has happened through sin, but neither is it to have mortality, [or the very possibility of death,] which the natural body had before it sinned. He does not say: “He that raised up Christ Jesus from the dead shall quicken also your  dead bodies” (although he had previously said, “the body is dead” ); but his words are: “He shall quicken also your mortal bodies;” so that they are not only no longer dead, but no longer mortal [or capable of dying], since the natural is raised spiritual, and this mortal body shall put on immortality, and mortality shall be swallowed up in life.