The warnings that the author of Hebrews gives about abandoning Christ are real warnings. The potential for apostasy and condemnation is not merely hypothetical. People really do break the covenant.
Hebrews 3:16–17 proves that people really can and really do break the covenant with God. The people with whom God was angry in the wilderness were not those who were outside the covenant. They were the ones who left Egypt with Moses and pledged at Sinai to enter into covenant and obey all of God’s laws (Ex. 19). They really were a part of God’s covenant, and yet they broke that covenant, and thus forsook all of the blessings that were promised in it. The book of Hebrews uses this story as a basis for warning Christians to persevere, thereby proving that the new covenant can be broken as well.
The fact that Hebrews gives real warnings and teaches that the new covenant can be broken might seem strange to those of us from a Reformed background. After all, are not the elect secure in their salvation? Surely it is not possible for the elect to lose their salvation?
The answer is yes, the elect are absolutely secure in their salvation. Nothing can separate us from the love of God in Christ Jesus (Rom. 8:38–39). No one can snatch us from the Father’s hand (John 10:28).
How then can these warnings be real? The answer lies in the concept of covenant. When God makes a covenant, He makes a covenant with both believers and unbelievers, with both the elect and the reprobate. This goes against much of the teaching we hear today, but it is the historic position of the Christian church. We often see the idea expressed in the distinction between the invisible Church and the visible church. The visible church consists of all professing believers. Some of them are true believers. Some of them confess Christ outwardly, but really lack saving faith. On the other hand, the invisible Church consists of true believers and true believers only.
The Reformed tradition recognizes that the Bible teaches both divine sovereignty and human responsibility. God is in control of all things. Human beings are responsible to keep the covenant. In the book of Hebrews, God gives us real warnings so that human responsibility is not invalidated, but rather sustained because the warnings motivate the invisible Church to keep the faith.
It is a sobering thought that every local church probably has people within it who profess Christ but in reality are far from the kingdom. Though we may not know who those people are, we must remain aware that they exist. Pray that all the people in your church may not only profess faith, but also possess it by God’s grace.