Hebrews 6

4 For it is impossible to bring back to repentance those who were once enlightened—those who have experienced the good things of heaven and shared in the Holy Spirit, 5 who have tasted the goodness of the word of God and the power of the age to come— 6 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.