Hebrews 6:4-6

4For [it is impossible to restore to repentance] those who have once been enlightened [spiritually] and who have tasted and consciously experienced the heavenly gift and have shared in the Holy Spirit,

5and have tasted and consciously experienced the good word of God and the powers of the age (world) to come,

6and then have fallen away—it is impossible to bring them back again to repentance, since they again nail the Son of God on the cross [for as far as they are concerned, they are treating the death of Christ as if they were not saved by it], and are holding Him up again to public disgrace.