The image of land is used by the writer of Hebrews to illustrate the Christian life. Just like land receives rain to produce the seeds that are sown, a believer will use the spiritual provisions received at salvation to produce a fruitful life. In the illustration a cultivated field will use the rain to produce a useful crop, while the same rain will produce useless thorns and thistles in a neglected field.
For each believer God provides "rain" in the form of the presence of the Holy Spirit, the teaching of the Word of God, the spiritual gifts, fellowship and encouragement through other believers, and much more, to assist the believer in the production of a fruitful and useful life. But, if these same spiritual provisions are neglected the believer will produce dead rituals, artificial application, religious activity and works of the flesh instead of the renewed mind, fruit of the spirit, manifestations of spiritual gifts and the advancement of the kingdom of God. This last list includes the "things that accompany salvation."
The believer is not being threatened with the loss of their salvation and eternity in the fires of hell. The believer is being warned that they are wasting their life and if they continue neglecting the provisions of God they will produce useless "thorns and thistles. This worthless crop, "In the end it will be burned." This teaching is similar to Paul's in First Corinthians:
"For no one can lay any foundation other than the one already laid, which is Jesus Christ. If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw, his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man’s work. If what he has built survives, he will receive his reward. If it is burned up, he will suffer loss; he himself will be saved, but only as one escaping through the flames."
- First Corinthians 3:11-14: