In our study of Hebrews chapter twelve, we look at how faith in the work of God produces hope both for the Jew and the Gentile. We will also see how faith in works leads to misery and despair.
"Therefore, since we are surrounded by such a great cloud of witnesses, let us throw off everything that hinders and the sin that so easily entangles. And let us run with perseverance the race marked out for us," NIV translation
In chapter 11, we saw a list of examples of people that had trusted in God. The list was presented as evidence that faith in God is justified based on God's past actions. The Jews understood that the character of God does not change and so He could be trusted in their lives just as He had been in the lives of their ancestors.
Paul goes on to tell them to get rid of everything that comes between them and that (faith) trust in God. The sin that he speaks of is a lack of trust in God.
The race that Paul speaks of is the Christian walk and it is not a competition to see who is the best Christian or a dash to get salvation or some other reward.
This race is a path that is marked out by the heroes of the faith that were on the list. He tells them to keep walking in that trust and not to stop or go back to the legalism/religion that had bound them.
He tells them to persevere meaning to continue on the path set before them even though it is difficult. These believers were constantly facing fellow Jews that wanted to apply parts of the Law of Moses to the grace of God. These people were called Judaizers and Paul fought them throughout his ministry. By calling them to continue, he helps us to see that some will not continue and, in fact, will fall from grace.
Unfortunately, this "falling from grace" is happening more and more in our world today. We have so many denominations (groups) that are based on differences in applying the Law of Moses to believers in Jesus Christ. This is sin and, as Paul said, it easily entangles. What may seem like a small rule or instruction easily becomes a part of some "doctrine" which causes us to trust less in the finished work of God and more on our efforts to please God. That is bad but an even worse effect of this legalism is division and judgment in the body of Christ. It leads to a false sense of superiority and a pride in our own efforts instead of a humble acceptance of the work of Christ.