NAS Hebrews 2:1 For this reason we must pay much closer attention to what we have heard, lest we drift away from it. 2 For if the word spoken through angels proved unalterable, and every transgression and disobedience received a just recompense, 3 how shall we escape if we neglect so great a salvation?
Heb 3:7 Therefore, as the Holy Spirit says, "Today, if you hear his voice, 8 do not harden your hearts as in the rebellion, on the day of testing in the wilderness, 9 where your fathers put me to the test and saw my works 10 for forty years. Therefore I was provoked with that generation, and said, 'They always go astray in their heart; they have not known my ways.' 11 As I swore in my wrath, 'They shall not enter my rest.'" 12 Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. 13 But exhort one another every day, as long as it is called "today," that none of you may be hardened by the deceitfulness of sin. 14 For we share in Christ, if indeed we hold our original confidence firm to the end. 15 As it is said, "Today, if you hear his voice, do not harden your hearts as in the rebellion."
NAS Hebrews 4:1 Therefore, let us fear lest, while a promise remains of entering His rest, any one of you should seem to have come short of it.
NAS Hebrews 4:6 Since therefore it remains for some to enter it, and those who formerly had good news preached to them failed to enter because of disobedience, 7 He again fixes a certain day, "Today," saying through David after so long a time just as has been said before, "Today if you hear His voice, Do not harden your hearts."
NAS Hebrews 4:11 Let us therefore be diligent to enter that rest, lest anyone fall through following the same example of disobedience.
NAS Hebrews 10:23 Let us hold fast the confession of our hope without wavering, for He who promised is faithful; 24 and let us consider how to stimulate one another to love and good deeds, 25 not forsaking our own assembling together, as is the habit of some, but encouraging one another; and all the more, as you see the day drawing near. 26 For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a certain terrifying expectation of judgment, and the fury of a fire which will consume the adversaries. 28 Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses. 29 How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace? 30 For we know Him who said, "Vengeance is Mine, I will repay." And again, "The Lord will judge His people." 31 It is a terrifying thing to fall into the hands of the living God.
NAS Hebrews 12:14 Pursue peace with all men, and the sanctification without which no one will see the Lord. 15 See to it that no one comes short of the grace of God; that no root of bitterness springing up causes trouble, and by it many be defiled; 16 that there be no immoral or godless person like Esau, who sold his own birthright for a single meal. 17 For you know that even afterwards, when he desired to inherit the blessing, he was rejected, for he found no place for repentance, though he sought for it with tears.
NAS Hebrews 12:25 See to it that you do not refuse Him who is speaking. For if those did not escape when they refused him who warned them on earth, much less shall we escape who turn away from Him who warns from heaven.