The writer of the book of Hebrew is unknown though some bible scholars ascribe authorship to Paul and some say it is Barnabas. This argument on authorship gave rise to a conclusion that made many believe the author is unknown. Though we may not know the exact author of this book, certain things are clear from the writings of the author.
First, he was a child of God with definite salvation experience. Second, he knew the levitical laws very well and understands the concept of the Mosaic law in details. Third, he wrote the book of Hebrews to Jewish believers who had their background in Judaism. The book of Hebrews is not in anyway lesser than other epistles.
With these said, the author gave a warning in the opening text enjoining believers to take heed so they won't have an evil heart of unbelief which leads to an outright departure from God. Meaning that it is possible for a believer to slip back into his vomit and eventually become godless to the point of missing out totally on the consummation of our salvation. It is a warning against backsliding.
If it weren't possible, the writer of Hebrew wouldn't have said so. It is one of those warning scriptures that every believer must heed. Scriptures such as this places a huge responsibility on man to ensure he remains and abides in the faith.
In verse 14 of the text under consideration, the author says, "For we are made partakers of Christ, IF we hold the beginning of our confidence stedfast unto the end". I want you to note the preposition "If". It introduces a condition into the statement. Let's analyse it quickly.
The author says we are made partakers of Christ If we hold on to our confidence steadfastly unto the end. The condition for partaking in Christ eternally is predicated upon staying in Christ till the end. It entails keeping the fervor of the Spirit and remaining in love with Christ and his ways.
Dearest, you can't live anywhow and still claim to have a hope of eternity in Christ. There is an "If" that is attached. Those who live in the flesh will not inherit the kingdom of God. You cannot claim to be under grace and live in sin. The understanding of our liberty in Christ is not an excuse to live any how.
Galatians 5:19-21 says, *"Now the works of the flesh are evident: sexual immorality, impurity,... [20] idolatry, sorcery, enmity, strife, jealousy, fits of anger... [21] envy...and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God (ESV)..