Paul, the author of almost half of the New Testament, talks about liberty and justification.
We are justified (made right with God, just if I’d never sinned) through Jesus.
Because of Jesus’s work on the cross we now have freedom and liberty from the bondage of Old Testament law. That is called grace. Those who know Jesus as Savior are no longer under the law, but under grace.
Paul also instructed Christ followers the only proper response to the gift of grace and mercy is to offer our bodies as living sacrifices.
We sometimes get that backwards, or as some say put the cart before the horse. Instead of allowing God’s justification to direct our behavior, we use his grace and mercy to justify our poor choices, since I have grace I no longer have to follow the law.
We say since I am under grace I am free to do this or that, when we should be saying, because of God’s grace and mercy I no longer want to exercise those liberties.
Instead of treating God’s grace and mercy as a welcome mat to wipe our shoes, it should cause us to fall on our knees in grateful and humble worship of the one who raised us to new life.