We Feel Sure of Better Things
F.F. Bruce: Once more, our author emphasizes that continuance is the test of reality. In these verses he is not questioning the perseverance of the saints; we might say that rather he is insisting that those who persevere are the true saints.
For it is impossible, in the case of those who have once been enlightened, who have tasted the heavenly gift, and have shared in the Holy Spirit, and have tasted the goodness of the word of God and the powers of the age to come, and then have fallen away, to restore them again to repentance, since they are crucifying once again the Son of God to their own harm and holding him up to contempt. For land that has drunk the rain that often falls on it, and produces a crop useful to those for whose sake it is cultivated, receives a blessing from God. But if it bears thorns and thistles, it is worthless and near to being cursed, and its end is to be burned.
Though we speak in this way, yet in your case, beloved, we feel sure of better things—things that belong to salvation. For God is not unjust so as to overlook your work and the love that you have shown for his name in serving the saints, as you still do. And we desire each one of you to show the same earnestness to have the full assurance of hope until the end, so that you may not be sluggish, but imitators of those who through faith and patience inherit the promises.