From gnm.org, a very good Catholic site.
I thought this really explained things well! Enjoy…
Somehow or other, it got into the Catholic psyche that we can earn our way into heaven by doing good works. This is one of the reasons why some Protestants mistakenly think we’re not saved, for as today’s first reading explains clearly, we overcome the power of sin and death to enjoy eternal life in heaven, not by doing good deeds and obeying Church rules, but by the grace of God through the redemptive sacrifice of Jesus and the power of his resurrection, and by placing our faith in that truth.
Good deeds and obedience are not tolls we pay to cross the bridge into heaven; they are fruits of the journey.
A good example of this is the Catholic teaching that it’s a mortal sin to miss Mass (we’ll go to hell if we don’t go to church). When the reasons behind this teaching are not considered, people assume that showing up on Sundays is all they have to do. That’s why Catholic churches have larger crowds than Protestant services but smaller collections. It’s why there’s poor attendance at other events of the parish and fewer people involved in ministries. Lots of folks attend Mass without being changed by their encounter with Christ in the Eucharist, because they’re only using Mass as an insurance policy.
If you sit in your garage for an hour a week, will you become a car? How about if you live in the garage every day and make engine noises? “Vrroom, vrroom!” Likewise, we can sit in church and even sound like Christians outside of church, but we only become free of the hellish forces of sin by wanting to receive the grace of Christ’s redemption. We can only become Christ-like by wanting to be changed during our personal encounters with him in the Eucharist.
Thus, the Church has always taught that if we prefer to stay out of church to stay away from Christ, we are killing our souls – we are committing mortal sin.
Trying to work our way into heaven by what we do without first having faith in Christ makes us like the scribes and Pharisees in today’s Gospel passage to whom Jesus said, “Woe!” We could make a large donation to build statues of the saints as decorations in the church, but if we are not learning from those very same saints, following their example of holiness, we are condemning ourselves by the contrast between our lives and theirs.
True faith motivates us to do good works, not because we want to get into heaven, but because we appreciate the sacrifice Jesus made for us on the cross and we know that with this faith we’re already receiving heaven. We want to do good works because we want to be like Jesus. We want to obey the rules of the Church because we understand their heavenly origin. Obedience and good deeds are the products of a faith that’s alive and truly holy.