“Once people have seen the light, gotten a taste of heaven and been part of the work of the Holy Spirit, once they've personally experienced the sheer goodness of God's Word and the powers breaking in on us - if then they turn their backs on it, washing their hands of the whole thing, well, they can't start over as if nothing happened. That's impossible. Why, they've re-crucified Jesus! They've repudiated Him in public! Parched ground that soaks up the rain and then produces an abundance of carrots and corn for its gardener gets God's "Well done!" But if it produces weeds and thistles, it's more likely to get cussed out. Fields like that are burned, not harvested.
If we give up and turn our backs on all we've learned, all we've been given, all the truth we now know, we repudiate Christ's sacrifice and are left on our own to face the Judgment - and a mighty fierce judgment it will be! If the penalty for breaking the law of Moses is physical death, what do you think will happen if you turn on God's Son, spit on the sacrifice that made you whole, and insult this most gracious Spirit? This is no light matter. God has warned us that he'll hold us to account and make us pay. He was quite explicit: "Vengeance is mine, and I won't overlook a thing" and "God will judge His people." Nobody's getting by with anything, believe me.
Hebrews 6:4-8; 10:26-31