It is by the Passion of Christ that we have been freed from the punishment due to sin

Surely he hath borne our infirmities and carried our sorrows.
Is. 53, 4

By the Passion of Christ we are freed from the liability to be punished for sin with the punishment that sin calls for, in two ways, directly and indirectly.

We are freed directly inasmuch as the Passion of Christ made sufficient and more than sufficient satisfaction for the sins of the whole human race. Now once sufficient satisfaction has been made, the liability to the punishment mentioned is destroyed.

We are freed indirectly inasmuch as the Passion of Christ causes the sin to be remitted, and it is from the sin that the liability to the punishment mentioned derives.

Souls in hell, however, are not freed by the Passion of Christ, because the Passion of Christ shares its effect with those to whom it is applied by faith and by charity and by the sacraments of faith. Therefore the souls in hell, who are not linked up with the Passion of Christ in the way just mentioned, cannot receive its effects.

Now although we are freed from liability to the precise penalty that sin deserves, there is, nevertheless, enjoined on the repentant sinner a penalty or penance of satisfaction. For in order that the effect of the Passion of Christ be fully worked out in us, it is necessary for us to be made of like form with Christ. Now we are made of like form with Christ in baptism by the sacrament, as is said by St. Paul, We are buried together with him by baptism into death (Rm. 6, 4). Whence it is that no penalty of satisfaction is imposed on those who are baptised. Through the satisfaction made by Christ they are wholly set free. But since Christ died once for our sins (1Pe. 3, 18), once only, man cannot a second time be made of like form with the death of Christ through the sacrament of baptism. Therefore those who, after baptism, sin again, must be made like to Christ in his suffering, through some kind of penalty or suffering which they endure in their own persons.

If death, which is a penalty due to sin, continues to subsist, the reason is this: The satisfaction made by Christ produces its effect in us in so far as we are made of one body with him, in the way limbs are one body with the head. Now it is necessary that the limbs be made to conform to the head. Wherefore since Christ at first had, together with the grace in his soul, a liability to suffer in his body, and came to His glorious immortality through the Passion, so also should it be with us, who are his limbs. By the Passion we are indeed delivered from any punishment as a thing fixed on us, but we are delivered in such a way that it is in the soul we first receive the spirit of the adoption of sons, by which we are put on the list for the inheritance of eternal glory, while we still retain a body that can suffer and die. It is only afterwards, when we have been fashioned to the likeness of Christ in his sufferings and death, that we are brought into the glory of immortality. St. Paul teaches this when he says, If sons, heirs also; heirs indeed of God, and joint heirs with Christ: yet so, if we suffer with him, that we may be also glorified with him (Rm. 8, 17).

(3 49 3.)