I came across a pretty good definition of the often bandied about term ‘LEGALISM’. There is not a Greek word in our NT that we can strictly understand as meaning what we refer to as legalism. So Paul invents different language to communicate this idea, like “works of the law”.
The erecting of specific requirements of conduct beyond the teaching of Scripture and making adherence to them the means by which a person is qualified for full participation in the local family of God, the church. — John Piper
This is where unbiblical exclusivism arises. I left a church that admittedly and proudly practices a ’separatist’ philosophy when it comes to extra-Biblical matters. There is no getting around the fact that the church does not include everyone. Peter refers to us as a “chosen race, a royal priesthood, a holy nation” ( I Peter 2:9). But exclusion of people from the church should never be taken lightly. It is a very serious matter. Schools and clubs and societies can set up any human regulations they wish in order to keep certain people out and preserve by rule a particular atmosphere. But the church is not man’s institution. It belongs to Christ. He is the head of the body, and he alone should set the entrance requirements.
This is FAR from being an exhaustive look at this topic. There are entire blogs devoted to the topic. I’m what would be best described as a recovering legalist. I’ve come out from it, but am too prone to fall back into my old ways. There is some sick comfort in it. A cheap replacement for the real life in Christ.

#1 by Ashley Pritchard on July 15th, 2009
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Legalism has such a strong hold on believers. I, like so many others, lost sight of our glorious Saviour. I was so focused on what I needed to do to merit favor. Their is a freedom in Christ, but not what legalists would think of it as. There is a freedom to be who we are in Christ. God did not create robots who are all alike. He gave us minds to know Him more, talents to give to His glory, and personalities to shine for Him. I would never want to give Him any less than all of me, but the real me….who I am.
#2 by Mary Fuller on July 17th, 2009
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There is great comfort in having a list of rules to follow, but it is also an invitation to both pride or false guilt. As you check off your list, you feel like you are getting somewhere in your Christian walk. Why, God is pretty lucky to have you on His team! And then, look at Sarah over there, she can only check off thirteen. Why, I’m Super Christian!!
Sometimes we look at the list and find that we can’t really ever measure up (this is the Holy Spirit at work within us). Satan and his minions stand beside us shouting accusations. In our discouragement we become unfruitful, knowing that God could never use a failure like us.
But God-confidences says that God has a purpose for us; He prepared good works beforehand for us to do. He has a mission, and what He’s called us to do, He will enable us to do. The reason? For the praise of HIS glory, not mine!
Legalism focuses on man. Freedom from the law focuses on God’s amazing grace in choosing the foolish things of this world to bring Him honor. Then it gives us God-confidence to accomplish the tasks He has set before us.