Hebrews 2:3
how shall we escape, if we neglect so great a salvation? which began to be declared by the Lord, and was confirmed to us by them that heard Him;
Hebrews 6:6
and the powers of the gospel-age, and yet fall away, should be renewed again to repentance: since they again crucify to themselves the Son of God, and make an open example of Him.
Hebrews 9:28
so Christ, having been once offered to bear the sins of many, shall appear the second time without sin, to those who are waiting for Him, unto salvation.
Hebrews 10:26-29
For if we sin wilfully after having received the knowledge of the truth, there remaineth no more sacrifice for sins;
Hebrews 12:25
See that ye reject not Him that speaketh; for if they escaped not, who rejected him that gave forth divine oracles on earth, much less shall we, if we turn away from Him that speaketh from heaven: