Galatians 5:12 :

I wish that those who disturb you would cut themselves off.

Paul must have been really upset when he wrote this letter. The thing that was coming against the Gospel message was very harmful to it. The words “cut themselves off” in this verse are often translated “castrate” in English. It’s pretty obvious that Paul was angry about those who were coming in harming the Gospel. Paul appears to be drawing on the imagery of circumcision here. I think you could paraphrase this verse like this:

“I wish that those who are messing you guys up would become so zealous about circumcision that they would just castrate themselves!”

I know of no other time in the Bible that Paul speaks with such anger. He has already committed the troublemakers to be accursed twice in chapter one and now this. It should be clear how important this issue is to us. The Bible leaves no room for us to treat this issue lightly. He says this problem is like yeast, that it sends people to hell, and it makes Paul so mad that He can hardly contain it. There is absolutely nothing optional or controversial about mixing the law in with Chrstianity.

God has committed Himself to punish those who cause His “little ones” to fall away with such severity that Jesus described it like this:

Matthew 18:6 :

but whoever causes one of these little ones who believe in me to stumble, it would be better for him that a huge millstone should be hung around his neck, and that he should be sunk in the depths of the sea.

Notice that Jesus said that this treatment would be “better.” God is still the God of the Old Testament. God never changes. The difference was Jesus. He died for you and I and God recognized that. Because there are those who purposely fight against Jesus, the “God of the Old Testament” will be back to do what must be done.