The writer of Hebrews was encouraging Jews to keep the faith. Many of them had been indoctrinated into Judaism and there was undoubtedly pressure on them to return. They were warned not to "drift away" (Heb 2:1) and not to "neglect so great a salvation" (:3). The gospel is "the power of God for salvation to every one who believes" (Ro 1:16) because "in it the righteousness of God is revealed from faith to faith" (:17). "It was at the first spoken through the Lord" (Heb 2:3) and "God [was] also bearing witness with them" (:4). Then "it was confirmed to us by those who heard" (:3). The author reminds them to "pay much closer attention to what we have heard" (2:1). He asks "how shall we escape?" (:3) if we ignore what we have heard. He warns about "falling away from the living God" (3:12) "whose house we are" (:6). Not "any one of you should seem to have come short of [the promise]" (4:1). We are "partakers of a heavenly calling" (3:1) and "partakers of Christ" (:14). It is because "we have had good news preached to us" (4:2). But it is necessary to "hold fast our confidence" (3:6) and "the beginning of our assurance" (:14). We are to cling to "the boast of our hope firm until the end" (:6). "Show the same diligence so as to realize the full assurance of hope until the end" (6:11). Remember that "faith is the assurance of things hoped for" (11:1). The author goes as far as to say "let us fear while the promise remains" (4:1). The danger is that "you be hardened by the deceitfulness of sin" (3:13). "Today, if you would hear His voice, do not harden your hearts" (Ps 95:7-8). "Take care, brethren, lest there should be any one of you an evil, unbelieving heart" (Heb 3:12).
There is a legal saying that possession is nine-tenths of the law. So if you "have once been enlightened and have tasted of the heavenly gift" (Heb 6:4) you have an entitlement. Also, if you "have been made partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come" (:5) you demonstrate ownership. These are heavenly, not worldly, characteristics. "Ground that drinks the rain which often falls upon it and brings forth vegetation useful to those for whose sake it is also tilled, receives a blessing from God" (:7). However, if they "then have fallen away, it is impossible to renew them again to repentance" (:6). "They have escaped the defilements of the world by knowledge of the Lord and Savior Jesus Christ" (2Pe 2:20). "It would be better for them not to have known the way of righteousness, than having known it, to turn away from the holy commandment delivered to them" (:21). Therefore, be mature and train yourselves to put the use of your spiritual senses into practice "to discern good and evil" (Heb 5:14).