By Origen of Alexandria
Christ has presented each Christian with the death of sin itself, a gift of faith, as it were, deriving from His own death. Sin can have no more freedom of action in people who believe themselves to be dead, crucified and buried with Christ, than in those who have suffered bodily death. They are therefore said to be dead to sin. This is why the Apostle says, "If we have died with Him, we believe we shall also live with Him." It is important to note the difference of expression: Paul does not say "we have lived" as he said "we have died," but "we shall live." This is his way of showing that death is at work in the present world, but not in the life to come, "when Christ is revealed. He is our life, hidden away in God." For the time being, therefore, as Paul himself teaches, "death is at work in us."
But it seems to me that this death that is at work in us has certain decisive moments. As with Christ there was the moment when Scripture says that "He cried out with a loud voice and gave up His spirit;" then there was the time when He was laid in the grave and its entrance was sealed up; and there was the morning when the women looked for Him in the tomb and did not find Him because He had already risen, though His actual resurrection was visible to none; so also in each of us who believe in Christ; there must be this threefold pattern of death.
First of all, Christ's death must be manifested in us by a verbal acknowledgment of our faith in Him, since "the faith that leads to righteousness in in the heart, and the confession that leads to salvation is on the lips." In the second place, we must show it by putting to death those passions which belong to the earth, as we carry Christ's death about with us wherever we go; this is what is meant by "death is at work in us." Thirdly, we have to proclaim Christ's death by showing that we ourselves have already risen from the dead and are walking in newness of life. To sum up briefly and clearly: the first day of death is when we renounce the world; the second, when we renounce the sins of the flesh; the third, the day of resurrection, when we are fully perfected in the light of wisdom. In each believer, however, these different stages and their degree of progress can be discerned and known only to God, to whom alone are revealed the secrets of our hearts.
Christ chose to empty Himself and take the form of a slave. He submitted to a despot's rule, and became obedient even to death. By that death He destroyed the lord of death, that is the devil, and set free all those whom death held captive. He tied up the Strong One, conquering him on the Cross, and broke into His house in the underworld, the stronghold of death. He then plundered his goods; in other words, He carried off the souls whom the devil held in bondage. This is the meaning of Christ's own parable in the gospel: "How can anyone break into a strong man's house and plunder his goods unless he begins by tying the strong man up?" First of all, then, He bound him on the Cross and so entered his house, that is the underworld. From there "He ascended on high, leading a host of captives," namely those who rose with Him from the dead and entered the holy city, the heavenly Jerusalem. Because of this, Paul rightly declares that "death no longer has any power to touch Him."
From the Commentary on Romans, 5.10: PG 14, 1048-52.