"4 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, 5 and have tasted the goodness of the word of God and the powers of the age to come, 6 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. 7 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. 8 But if it bears thorns and thistles, it is worthless and near to being cursed, and its end is to be burned."
Hebrews 6:4-8
The interpretation of these words which refers them to the possibility of a believer becoming a castaway, in the sense of being disqualified and thus losing his reward, seems, in our present state of spiritual understanding, to be the most likely one of all. We should bear in mind that the Apostle has already been referring in previous chapters to Israel's failure to enter into the Promised Land because of unbelief. Now, Israel was God's covenant people, and they were not finally disowned as to the inheritance of eternal life, but they lost the privilege of inheriting the land and were turned back into the wilderness. The parallel is therefore with His new covenant people, the Church, failing to lay hold of His promises for them and enter His destiny for them. The awful words 'it is impossible....' (4) must therefore refer to some significant crisis point in the sin of unbelief which is really a point of no return. Later on in Hebrews (10:26, 27) the Apostle speaks of 'sinning wilfully', and this, it would seem, refers to just such a point, when human sin passes beyond the stage of having in its composition the element of frailty and weakness, 'All we like sheep have gone astray', which makes sin forgivable, and becomes pure rebellion. This is very frightening, for who is to draw the line between the one and the other? It may be that God draws the line when we are not conscious of His doing so, and says 'Enough!', and swears in His wrath, 'They shall not enter into My rest'. Certainly, the only way of avoiding the danger of sinning wilfully is to strive with might and main, and inasmuch as lieth in us, not to sin at all. This is the point of the warning here. Therefore, let us go on, lest we go back.