Only way and no other

The exhortations against apostasy 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 Savior; 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 comes unto Christ, he will in no wise cast out.

Hebrews 10:26-31

 ²⁶ If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, ²⁷ but only a fearful expectation of judgment and of raging fire that will consume the enemies of God. ²⁸ Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses. ²⁹ How much more severely do you think someone deserves to be punished who has trampled the Son of God underfoot, who has treated as an unholy thing the blood of the covenant that sanctified them, and who has insulted the Spirit of grace? ³⁰ For we know him who said, “It is mine to avenge; I will repay,” and again, “The Lord will judge his people.” ³¹ It is a dreadful thing to fall into the hands of the living God.