Read Hebrews 6:6 Using Other Translations
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.
and then have fallen away, to restore them again to repentance, since they are crucifying once again the Son of God to their own harm and holding him up to contempt.
and who then turn away from God. It is impossible to bring such people back to repentance; by rejecting the Son of God, they themselves are nailing him to the cross once again and holding him up to public shame.