Hebrews 2:3
how can we, of all people, expect to escape, if we disregard so great a Salvation? It was the Master who at the outset spoke of this Salvation, and its authority was confirmed for us by those who heard him,
Hebrews 6:6
if those, I say, fell away, it would be impossible to bring them again to repentance; they would be crucifying the Son of God over again for themselves, and exposing him to open contempt.
Hebrews 9:28
so it is with the Christ. He was offered up once and for all, to 'bear away the sins of many'; and the second time he will appear--but without any burden of sin--to those who are waiting for him, to bring Salvation.
Hebrews 10:26-29
Remember, if we sin willfully after we have gained a full knowledge of the Truth, there can be no further sacrifice for sin;
Hebrews 12:25
Beware how you refuse to hear him who is speaking. For, if the Israelites did not escape punishment, when they refused to listen to him who taught them on earth the divine will, far worse will it be for us, if we turn away from him who is teaching us from Heaven.