#What is impossible for those who were sharers in the Holy Spirit, but then fell away, to do?

It is impossible for those who were sharers in the Holy Spirit, but then fell away, to be restored again to repentance. [6:4-6]

#Why are these people not able to be restored to repentance?

They are not able to be restored because they have crucified for themselves the very Son of God. [6:6]