We have been studying the book of Galatians this term at COTC and the major theme which Paul drives home passage by passage is the insidious and damaging error of legalism
Gal 3:3 Are you so foolish? After beginning with the Spirit, are you now trying to attain your goal by human effort?
I think that very few of us are in danger of legalism in terms of our justification – in terms of how we start as Christians. But our great danger is that we fall into legalism when it comes to sanctification – in terms of our growth as Christians. And the implications of Legalism in terms of our attitudes to ourselves, to guilt, and even to the Gospel are serious.
“Legalism is common to us all In one degree or another because it is human nature. We want to do everything on our own; we want to be self-sufficient. we want to feel like we are in control. So when it comes to good works we look at them as the way in which we can control our salvation. If we are bad, we forfeit salvation; if we are good, we earn it.”
Or as John Piper puts it “Human effort is the insubordinate, self-determining ego which in religious people responds to God’s Word not with reliance on the Spirit but with reliance on self. It can produce a very rigorous morality, but it nullifies grace and removes the stumbling block of the cross.”