Matthew Henry on Hebrews 10:26-31

The exhortations against apostacy and to perseverance, are urged by many strong reasons. The sin here mentioned is a total and final falling away, when men, with a full and fixed will and resolution, despise and reject Christ, the only Saviour; despise and resist the Spirit, the only Sanctifier; and despise and renounce the gospel, the only way of salvation, and the words of eternal life. Of this destruction God gives some notorious sinners, while on earth, a fearful foreboding in their consciences, with despair of being able to endure or to escape it. But what punishment can be sorer than to die without mercy? We answer, to die by mercy, by the mercy and grace which they have despised. How dreadful is the case, when not only the justice of God, but his abused grace and mercy call for vengeance! All this does not in the least mean that any souls who sorrow for sin will be shut out from mercy, or that any will be refused the benefit of Christ's sacrifice, who are willing to accept these blessings. Him that cometh unto Christ, he will in no wise cast out.