… ⁶ and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God and put Him to open shame.

“Crux of the matter” is the best way to describe this verse. First, if this refers to those who are not genuine believers, this passage would teach that a person who comes close to salvation and then turns away, will never get a second chance to come back again to that point. That would mean there are some people who are un-savable. However, it is hard to avoid the description of verses 4-5 as referring to genuine Christians.

If this passage is about genuine believers (saved, redeemed, regenerated, adopted, given eternal life, enlightened, tasted of the heavenly gift, made partakers of the Spirit, etc.)—AND IF they fall away, then there is no second chance. There is no hope for ever being renewed or restored. The falling away here clearly has the sense of abandoning Christ and returning to the old way of religion by laws and ritual, that is, the natural man-made, man-earning, form of spirituality. And the entire book of Hebrews is about the superiority of Christ over all such systems and efforts.

Let me emphasize this: if one believes he can lose his salvation, then there is no hope for being re-saved! The reason given is that to renew a person to repentance would require another sacrifice of Christ. But that is absolutely impossible. He died once for all, as we will soon find out (see 7:27, 10:10-14). To put Christ to death again, if only in one’s theological imagination, would ironically bring us right back to the Levitical style priesthood where the sacrifices are repeated. If Christ needs to be crucified again, then that would mean the “supposed” first death of Christ was not good enough, not perfect. Then He would be no greater than the priests of the Old Testament. Remember, we were about to read of the Melchizedek priesthood, but the readers were not mature enough to understand that yet. So, this digression needs to be addressed first, the false notion that one could lose their salvation!

Observe very carefully that the notion of crucifying Christ again would bring great shame on Him! As 10:29 puts it, that would be like one who “trampled underfoot the Son of God.” This shows how utterly absurd is the idea of a Christian falling away and then being renewed to repentance again. In short, if the first time of salvation didn’t work, then getting saved a second time will not either. In fact the idea is patently self-defeating.