Legalism is seeking to achieve forgiveness from God and acceptance by God through obedience to God. In other words, a legalist is anyone who behaves as if they can earn God's approval and forgiveness through personal performance.
The Cross Centered Life
legalism has its origin in self-worship. If people are justified through their obedience to the law, then they merit praise, honor, and glory. Legalism, in other words, means the glory goes to people rather than God.
Legalism claims that the death of Jesus on the cross was either uneccessary or insuficient. It essentially says to God, "Your plan didn't work. The cross wasn't enough and I need to add my good works to it to be saved."
One by one, Stuart added more and more spiritual activities to his life. Each was good. Some were vital. Yet without realizing it, Stuart allowed a dangerous shift to take place in his mind and heart. What God had intended to be a means of grace, Stuart had changed into a means of earning grace. Instead of being a further expression of his confidence in God's saving work in his life, his spiritual activities became spinning plates to maintain.
The shift is plainly seen on Sunday mornings. On one Sunday, Stuart sings and praises God with evident sincerity and zeal. Why? Because he's just had a really good week. Not a single plate has wobbled.
But on another Sunday, following a week in which several plates fell, Stuart is hesitant to approach God. He finds it difficult to worship freely, because he feel that God disapproves of him. His confidence is no longer in the gospel; it's in his own performance, which hasn't been so great lately.