The Zondervan dictionary of Bible themes defines legalism as “the belief that salvation demands or depends upon total obedience to the letter of the law. Examples of legalism include an excessive concern for minute details of the will coupled with a neglect of its fundamental concerns, and a preoccupation with human legal traditions.“
The danger of this sinful attitude: one who is committed to it could spend an eternity in hell and can be responsible for sending others there too. We see this in Matthew 23:13 & 15: ““But woe to you, scribes and Pharisees, hypocrites! For you shut the kingdom of heaven in people’s faces. For you neither enter yourselves nor allow those who would enter to go in.” “Woe to you, scribes and Pharisees, hypocrites! For you travel across sea and land to make a single proselyte, and when he becomes a proselyte, you make him twice as much a child of hell as yourselves.”
Legalism is more worried about rules than the heart.
You might be a legalist if you condemn someone’s sin while ignoring and denying your own.
In John 7:19, Jesus asked the Jewish people why they were seeking to kill him. They thought Jesus was guilty enough of something that he should be put to death, but there was no justification since he was sinless.
So they were condemning a sinless man to death at the same time they were guilty of not keeping the law of Moses.
They ignored their own sin while falsely condemning Jesus. While we know that Jesus did not sin, his purity here is actually irrelevant to the Jewish peoples’ argument because they should have looked at themselves first before accusing him.
Not only did they ignore their sin but they also denied it. In verse 20, they blast, “You have a demon! Who is seeking to kill you?” They wouldn’t even admit their own guilt of wanting to kill him! But Jesus, in his infinite knowledge as God, knew their hearts, their intentions, and their guilt.
It is so easy to do the exact same thing – quickly condemn other people for their sin, while ignoring and denying our own. This is legalism– holding other people up to the laws of God while somehow exempting yourself from them.