Also, the nature of the exhortations in chapter 13 shows they are obviously intended for believers. There is no attempt to apply them to two different groups. In fact, in the entire epistle, the warning passages are never introduced with any transition that indicates the author is shifting his attention to a different group within the readership. To imply otherwise is artificial and therefore disruptive to the flow of the text.

1. They are addressed using first person plural pronouns, which shows the author identifies with them as believers (“we” in 2:1, 3; 3:14, 19; 4:3; 10:26, 30, 39; 12:28; and “us” in 4:1, 2, 11; 6:1, 3; 10:26, 30, 39; 12:28).
2. They are also called “brethren” (3:12). Just as in the non-warning sections, this clearly shows their common position in God’s family.
3. They have believed (4:3; 10:39). This speaks of an unqualified faith in Christ as Savior. They are not said to have almost believed, or believed in an insufficient way.
4. They have Christian confidence (3:14; 10:35). This refers to their assurance of the benefits of Christ’s provisions. They are therefore told to hold fast (3:14; 4:14; 10:23) and endure (10:36) in that confidence.
5. They are in danger of denying their faith. They have not yet, but could “drift away” (2:1), depart “from the living God” (3:12), “fall away” (6:6), “draw back” (10:39), or “turn away” (12:25). All such language demands a point of departure from which they can fall. The only such point in the epistle is Jesus Christ and their confession of Him.
6. They are encouraged to enter God’s rest (4:11) and go on to maturity (6:1). As in the Old Testament, “rest” refers not just to the reception of God’s promise, but the enjoyment of it. It is only a privilege of believers, as is the possibility of growth into maturity.
7. They suffered for their faith after they were “illuminated” (10:32-34). They were able to endure this persecution because they knew they had a heavenly possession (10:34).
8. They are never told to believe in Christ, which we would expect if they are unbelievers. It would be a travesty for the author to omit this. Instead, he says the epistle was written to exhort or encourage the readers (13:22).
9. They are described as having experienced the blessings that come with faith in Christ. The most convincing evidence is from 6:4-5: They were “enlightened,” had “tasted the heavenly gift,” had “become partakers of the Holy Spirit,” and had “tasted the good word of God and the powers of the age to come.” Any attempt to apply these descriptions to unbelievers forces the text at the expense of good exegesis and the plain sense of the language. They had also “received the knowledge of the truth” (10:26), were “sanctified” (10:29), “know” God (10:30), were “illuminated” (10:32), and by implication are called “just” or righteous (10:38).
10. They are given Old Testament analogies that in the past and now in their present apply to God’s chastening of His people. In 3:16 Psalm 95 is used of the redeemed who came out of Egypt and so obviously applies to the redeemed readers. In 10:30 Deuteronomy 32:36 speaks of God judging “His people.” That this applies to believers is obvious in 10:31 where there is the prospect of falling “into” the hands of God. They can not fall out of His hands.
11. They are exhorted to “serve God acceptably with reverence and godly fear” (12:28), something impossible for unbelievers.
12. They face the prospect of rewards conditioned on their faithful perseverance and obedience. They can be “partakers of Christ” (3:14), can enter God’s rest (4:9, 11), can have “an enduring possession . . . in heaven” (10:34), can receive a “great reward” (10:35), and can “receive a kingdom” (12:28).

Probably the reason so many interpret these warnings as to unbelievers is because of the severe judgments threatened, especially those that mention fire. Should the mention of fire automatically imply the threat of eternal damnation? Absolutely not! But that is another study. Let us who believe take to heart both the exhortations to grow in our confession of Christ and the warnings about neglecting that growth. All of Hebrews can apply to us.

from gracelife.org