St. Paul taught that those in the state of sin cannot inherit the Kingdom of Heaven. Now the works of the flesh are plain: fornication, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, party spirit, envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God.  (Galatians 5:19-21)

Furthermore, Paul taught the forgiveness of sins through Christ Jesus.  All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation; that is, in Christ God was reconciling the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation.  So we are ambassadors for Christ, God making his appeal through us. We beseech you on behalf of Christ, be reconciled to God. (2 Corinthians 5:18-21)  “The ministry of reconciliation” Paul refers to is the authority given to the apostles by Christ to forgive sins in His name.   Jesus said to them again, “Peace be with you. As the Father has sent me, even so I send you.”  And when he had said this, he breathed on them, and said to them, “Receive the Holy Spirit.  If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained.” (John 20: 21-23)  The power to forgive sins resides in Christ and is exercised through those having apostolic authority vested in them by Christ and His designates.  Those having apostolic authority are the “us” Paul speaks.   The “you” are the laity (of Corinth).

Paul clearly preached the forgiveness of sins through the sacrament of reconciliation administered by those having apostolic authority vested in them by Christ and designates.