I know many will not like what I tell you, but it is God's Word, not mine!!
The sin spoken of here is the deliberate turning back to Judaism. Which is a "religion" started in Babylon. I have no prejudice to any who practice Judaism. I want to make that clear. God wanted His people to follow Christ. Hebrews 10:20 By a new way and living way which He hath cansesecrated for us, through the veil [ SEE VERSE 6:19-20] Matt 27:51 that is to say, His flesh; You have to go back to the beginning of the chapter to understand. Here it is clear that blood sacrifice is no longer the way to salvation.
As I have clearly said, I am not against any religion, and fought very hard in a foreign county for the right to worship as you please. These people do no one any harm in their practice. It is simply God's Word, and I could not be silent.