Heb 6:4-6
"For it is impossible, in the case of those who have once been enlightened, who have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, and then have fallen away, to restore them again to repentance."
The most debated text in Hebrews. The five privileges of those who fall: enlightened, tasted the heavenly gift, shared in the Spirit, tasted the Word, tasted the powers of the age to come. The impossibility of restoration: not because God does not forgive, but because the apostate crucifies Christ again — a conscious and definitive rejection.