“For freedom Christ has set us free; stand firm therefore, and do not submit again to a yoke of slavery.
“Look: I, Paul, say to you that if you accept circumcision, Christ will be of no advantage to you. I testify again to every man who accepts circumcision that he is obligated to keep the whole law. You are severed from Christ, you who would be justified by the law; you have fallen away from grace. For through the Spirit, by faith, we ourselves eagerly wait for the hope of righteousness. For in Christ Jesus neither circumcision nor uncircumcision counts for anything, but only faith working through love.” Galatians 5:1-6
What we believe defines our spiritual reality. Believe the promises of God and you receive His kingdom. Replace those promises with something else, and you are severed from the kingdom. It is NOT a matter of failing to do works to be saved.
For many Christians this is an uncomfortable and unresolved subject. Can people who were once saved be lost? There are several places in the new testament that at least infer that it can happen. In this passage Paul says “you are severed from Christ” if you seek to be justified by works. Paul also talks about being cut off from Christ after being grafted in when he sent this warning to the Romans:
“Then you will say, ‘Branches were broken off so that I might be grafted in.’ That is true. They were broken off because of their unbelief, but you stand fast through faith. So do not become proud, but fear. For if God did not spare the natural branches, neither will he spare you. Note then the kindness and the severity of God: severity toward those who have fallen, but God’s kindness to you, provided you continue in his kindness. Otherwise you too will be cut off. And even they, if they do not continue in their unbelief, will be grafted in, for God has the power to graft them in again.” (Romans 11:19-23).
It all comes down to faith and unbelief. Christ died for the sins of the whole world. Believe, and you enter the invisible kingdom. Refuse to believe, or stop believing, and you leave it behind. As Jesus said, “The one who endures to the end will be saved.” (Matthew 11:24).