Legalism is a distortion of obedience.  It is guilty of:-

• a skewed purpose, seeing good works as ways of earning God’s favour;
• an arrogant attitude, leading to contempt for those who do not make the same effort to gain God’s favour;
• a loveless focus on self, squeezing kindness and compassion out of the heart.

In the New Testament, legalism is found in two main forms:-

• Jesus confronted legalism in the Pharisees, who boasted of their privileged status as children of Abraham and their law-keeping.  They (a) focused on the minute details of external behaviour, disregarding what was most important (Mt 23:23f); (b) negated the law’s spirit and aim, Mt 15:3-9; 23:16-24; (c) treated their own traditions as if they had the status of divine law, thus binding men’s consciences (Mk 2:16-3:6; 7:1-8; (d) were hypocritical at heart, caring more about human approval, rather than divine, (Lk 20:45-47; Mt 6:1-8; 23:2-7.

• Paul confronted legalism in the Judaizers, who taught that every Gentile convert must become a Jew by circumcision and observance of holy days and ritual laws.  The apostle (a) condemned the false teachers at Galatia, who denied the all-sufficiency of Christ and his work, (Gal 3:1-3; 4:21; 5:2-6); (b) similarly criticised those in Colosse for their ‘Christ-plus’ formula for spiritual fullness (Col 2:8-23).

The problem with legalism in all its forms is that, far from enriching our relationship with God, it actually diminishes it.  Indeed, it puts that relationship in jeopardy by taking our focus away from Christ.  It feeds our pride while starving our souls.  It is to be avoided like the plague.

Based on J. I. Packer, Concise Theology