11 Wherefore, even as consecration proclaims and confirms this union with Christ, so does expiation begin that same union by washing away faults, and perfect it by participating in the sufferings of Christ, and consummate it by offering victims for the brethren. And this indeed was the purpose of the merciful Jesus, when He showed His Heart to us bearing about it the symbols of the passion and displaying the flames of love, that from the one we might know the infinite malice of sin, and in the other we might admire the infinite charity of Our Redeemer, and so might have a more vehement hatred of sin, and make a more ardent return of love for His love.
Source: Miserentissimus Redemptor (Vatican.va)