Hebrews 2:3
How shall we escape, if we neglect so great a salvation, which began to be spoken by the Lord, and was confirmed to us by them that had heard him?
Hebrews 6:6
And have fallen away, to renew them again unto repentance, seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
Hebrews 9:28
So Christ also, having been once offered to bear the sins of many, will appear the second time, without sin, to them that look for him, unto salvation.
Hebrews 10:26-29
For when we sin wilfully after receiving the knowledge of the truth, there remaineth no more sacrifice for sins,
Hebrews 12:25
for if they escaped not who refused him that delivered the oracle on earth, much more shall not we, who turn away from him that speaketh from heaven: