15 "Appeased by this oblation, the Lord grants grace and the gift of repentance, and forgives iniquities and sins, however great." The reason of this is given by the same Council in these words: "For there is one and the same Victim, there is present the same Christ who once offered Himself upon the Cross, who now offers Himself by the ministry of priests, only the manner of the offering being different."
Source: Ad Catholici Sacerdotii (Vatican.va)