19* On the evening of that day, the first day of the week, the doors being shut where the disciples were, for fear of the Jews, Jesus came and stood among them and said to them, “Peace be with you.” 20 When he had said this, he showed them his hands and his side. Then the disciples were glad when they saw the Lord. 21* Jesus said to them again, “Peace be with you. As the Father has sent me, even so I send you.” 22* And when he had said this, he breathed on them, and said to them, “Receive the Holy Spirit. 23* If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained.” RSV (Harmony Media, welcome to the Catholic Church, version 3.0, 2005)
Who is Jesus speaking to? What is the context? He has come from the Father, with a commission, and now is commissioning the apostles, with the authority of the Father, through the power of the Holy Spirit. They have the authority to forgive sins because of this anointing of the spirit (the breath). They also have the authority to deny forgiveness as the retention implies withholding not only forgiveness but absolution, since sins not retained are absolved, no longer held against the sinner. He is not imparting this authority to all believers (who nonetheless are obliged to personally forgive those who injure them) but to the apostles whom he has chosen and prepared (the Last Supper discourse being the most immediate preparation) them to receive the Spirit and the consequent authority. Absolution is implied in the use of retention. Absolution means the sins are gone.