Hebrews 2:3
Which having begun to be spoken by the Lord, was confirmed to us by those who heard him;
Hebrews 6:6
and then fallen away, it is impossible to renew them again unto repentance. For they repeatedly crucify to themselves the Son of God afresh, and expose him to an open shame.
Hebrews 9:28
so also the Christ, after being once for all offered to bear the sins of many, will appear a second time, without sin, to those who wait for him for salvation.
Hebrews 10:26-29
For if we sin wilfully, after we have received the knowledge of the truth, there no longer remains any other sacrifice for sins,
Hebrews 12:25
See that you do not refuse him who is speaking. For if they did not escape punishment when they refused to listen to their instructor on earth, much less shall we escape if we turn away from him who is teaching us from heaven;