31 But besides bearing in a Christian spirit the inescapable annoyances and sufferings of this life, the faithful ought also take the initiative in doing voluntary acts of penance and offering them to God. In this they will be following in the footsteps of our divine Redeemer who, as the Prince of the Apostles said, "died once for sins, the Just for the unjust; that he might bring us to God. Put to death indeed in the flesh, he was brought to life in the spirit."(31) "Since, therefore, Christ has suffered in the flesh," it is only fitting that we be "armed with the same intent."(32)
Source: Paenitentiam Agere (Vatican.va)