Hebrews 6:1-6 (NKJV)
The Peril of Not Progressing
6 Therefore, leaving the discussion of the elementary principles of Christ, let us go on to [a]perfection, not laying again the foundation of repentance from dead works and of faith toward God, 2 of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment. 3 And this [b]we will do if God permits.
4 For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come, 6 [c]if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame.