Thirsting Souls Bible Teaching

(Heb 6:4) “For [it is] impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, (5) And have tasted the good word of God, and the powers of the world to come, (6)  If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.”   Part Two: Ok. I know the Bible again and again teaches salvation is eternal, never ending. If this verse cannot be saying that, then what is it saying. Notice  the two little words in brackets, italics in the King James Bible, “it is”. Those, as in other places, were inserted to help clarify. In this case, it doesn’t. The words could read, “if it would be”.