I.e., the blood of Jesus isn't sufficient to forgive sins. You still gotta take some licks for the stuff that's even beyond the reaches of the cross.
According to Scripture, Jesus Christ Granted the Apostles His Authority to Forgive Sins. In John 20:23 - Jesus says, "If you forgive the sins of any, they are forgiven. If you retain the sins of any, they are retained." In order for the apostles to exercise this gift of forgiving sins, the penitents must orally confess their sins to them because the apostles are not mind readers. The text makes this very clear. The successors of the Apostles are the priests in the Catholic and Orthodox Churches.
Where ignorance is bliss, tis folly to be wise.