Hebrews 6:4-6

For how can those who abandon their faith be brought back to repent again? They were once in God's light; they tasted heaven's gift and received their share of the Holy Spirit; they knew from experience that God's word is good, and they had felt the powers of the coming age. And then they abandoned their faith! It is impossible to bring them back to repent again, because they are again crucifying the Son of God and exposing him to public shame.