More on how this works

The previous quotation, taken on its own, might give the impression that sin is stronger than purity. But this really gets back at the root of St. Paul's observations about the relationship between sin and the law. We can make purity into a new law, or an expression of the law, which puts us right back in the state of needing to adhere to every jot and tittle to remain in a state of righteousness. None of us can ever do it. So in that sense, a drop of sewage pollutes our whole lives.

But we have a Savior who has delivered us from the law, including the temptation to bind ourselves to a new law. Our purity is now not an effort to make ourselves righteous, but a loving response to both the righteousness and grace of Christ at work in our lives. That drop of impurity still has a soiling effect on us, to which we are not immune. The sacrament of Reconciliation provides a means for us to hear Christ express loving forgiveness as we turn away from our sin to be more fully transformed in Him.