For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
Heb 10:27 But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
L Berkhof Systematic Theology
The Unpardonable Sin. Several passages of Scripture speak of a sin that cannot be forgiven, after which a change of heart is impossible, and for which it is not necessary to pray. It is generally known as the sin or blasphemy against the Holy Spirit. The Saviour speaks of it explicitly in Mat 12:31,32 and parallel passages; and it is generally thought that Heb 6:4-6; 10:28,27, and John 5:16 also refer to this sin.
a. Unwarranted opinions respecting this sin. There has been quite a variety of opinions respecting the nature of the unpardonable sin. (1) Jerome and Chrysostom thought of it as a sin that could be committed only during Christ's sojourn on earth, and held that it was committed by those who were convinced in their hearts that Christ performed His miracles by the power of the Holy Spirit, but in spite of their conviction refused to recognize these miracles as such and ascribed them to the operation of Satan. However, this limitation is entirely unwarranted, as the passages in Hebrews and 1 John would seem to prove. (2) Augustine, the Melanchtonian dogmaticians of the Lutheran Church, and a few Scottish theologians (Guthrie, Chalmers) conceived of it as consisting in impoenitentia finalis, that is, impenitence persisted in to the end. A related view is that expressed by some in our own day, that it consists in continued unbelief, a refusal up to the very end to accept Jesus Christ by faith. But on this supposition it would follow that every one who died in a state of impenitence and unbelief had committed this sin, while according to Scripture it must be something of a very specific nature. (3) In connection with their denial of the perseverance of the saints, later Lutheran theologians taught that only regenerate persons could commit this sin, and sought support for this view in Heb 6:4-6. But this is an un-Scriptural position, and the Canons of Dort rejected, among others, also the error of those who teach that the regenerate can commit the sin against the Holy Spirit.
b. The Reformed conception of this sin. The name "sin against the Holy Spirit" is too general, for there are also sins against the Holy Spirit that are pardonable, Eph 4:30. The Bible speaks more specifically of a "speaking against the Holy Spirit," Mat 12:32; Mar 3:29; Luk 12:10. It is evidently a sin committed during the present life, which makes conversion and pardon impossible. The sin consists in the conscious, malicious, and wilful rejection and slandering, against evidence and conviction, of the testimony of the Holy Spirit respecting the grace of God in Christ, attributing it out of hatred and enmity to the prince of darkness. It presupposes, objectively, a revelation of the grace of God in Christ, and a powerful operation of the Holy Spirit; and, subjectively, an illumination and intellectual conviction so strong and powerful as to make an honest denial of the truth impossible. And then the sin itself consists, not in doubting the truth, nor in a simple denial of it, but in a contradiction of it that goes contrary to the conviction of the mind, to the illumination of the conscience, and even to the verdict of the heart. In committing that sin man wilfully, maliciously, and intentionally attributes what is clearly recognized as the work of God to the influence and operation of Satan. It is nothing less than a decided slandering of the Holy Spirit, an audacious declaration that the Holy Spirit is the spirit of the abyss, that the truth is the lie, and that Christ is Satan. It is not so much a sin against the person of the Holy Spirit as a sin against His official work in revealing, both objectively and subjectively, the grace and glory of God in Christ. The root of this sin is the conscious and deliberate hatred of God and of all that is recognized as divine. It is unpardonable, not because its guilt transcends the merits of Christ, or because the sinner is beyond the renewing power of the Holy Spirit, but because there are also in the world of sin certain laws and ordinances, established by God and maintained by Him. And the law in the case of this particular sin is, that it excludes all repentance, sears the conscience, hardens the sinner, and thus renders the sin unpardonable. In those who have committed this sin we may therefore expect to find a pronounced hatred of God, a defiant attitude to Him and all that is divine, delight in ridiculing and slandering that which is holy, and absolute unconcern respecting the welfare of their soul and the future life. In view of the fact that this sin is not followed by repentance, we may be reasonably sure that they who fear that they have committed it and worry about this, and who desire the prayers of others for them, have not committed it.
c. Remarks on the passages in the Epistles that speak of it. Except in the Gospels, this sin is not mentioned by name in the Bible. Thus the question arises, whether the passages in Heb 6:4-6; 10:25,27,29, and 1Jo 5:16 also refer to it. Now it is quite evident that they all speak of an unpardonable sin; and because Jesus says in Mat 12:31, "Therefore..., thereby indicating that there is but one unpardonable sin, it is but reasonable to think that these passages refer to the same sin. It should be noted, however, that Heb 6 speaks of a specific form of this sin, such as could only occur in the apostolic age, when the Holy Spirit revealed itself in extraordinary gifts and powers. The fact that this was not borne in mind, often led to the erroneous opinion that this passage, with its unusually strong expressions, referred to such as were actually regenerated by the Spirit of God. But Heb 6:4-6, while speaking of experiences that transcend those of the ordinary temporal faith, yet do not necessarily testify to the presence of regenerating grace in the heart.
They are in covenant in the sense that they are subject to the ministrations of the covenant. They are consistently admonished and exhorted to live according to the requirements of the covenant,. The Church treats them as covenant children, offers them the seals of the covenant, and exhorts them to a proper use of these. They are the guests who are first called to the supper, the children of the kingdom, to whom the Word must be preached first of all, Mat 8:12; Luk 14:16-23; Act 13:46.