Hebrews 6:4-6

4 For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come, 6 and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God and put Him to open shame.