The Westminster Confession follows this wording in Chapter 29:8. "Although ignorant and wicked men receive the outward elements in this sacrament: yet they receive not the thing signified thereby, but by their unworthy coming thereunto are guilty of the body and blood of the Lord to their own damnation. Wherefore, all ignorant and ungodly persons, as they are unfit to enjoy communion with Him, so are they unworthy of the Lord’s table; and cannot, without great sin against Christ while they remain such, partake of these holy mysteries, or be admitted thereunto".
Some believe that the Westminster Divines were referring here to unbelievers. This is not the case, however, they distinguish ignorant as well as wicked men. This does not absolutely define such as unbelieving, it refers to their fitness for this duty i.e. knowledge and discerning the Lord's body. We can see this by comparing with other uses of this verse in the Westminster Standards. In the Larger Catechism it refers to the ability to examine oneself in this matter. Question 173: May any who profess the faith, and desire to come to the Lord’s Supper, be kept from it? Answer: Such as are found to be ignorant or scandalous, notwithstanding their profession of the faith, and desire to come to the Lord’s Supper, may and ought to be kept from that sacrament, by the power which Christ hath left in his church, until they receive instruction, and manifest their reformation (see also Q170, 171, 174 and 177 - Q112 indicates that it relates to the right use of the sacraments).
The Shorter Catechism asks:
Q. 97. What is required to the worthy receiving of the Lord’s supper?
A. It is required of them that would worthily partake of the Lord’s supper, that they examine themselves of their knowledge to discern the Lord’s body, of their faith to feed upon him, of their repentance, love, and new obedience; lest, coming unworthily, they eat and drink judgment to themselves.
The fact that the word judgement is used here as well as offered in the margin means that the words are interchangeable. The word damn in older usage could just mean to condemn someone for something as well as its most solemn meaning. Romans 14:23 in the AV is an example of this - they did not always use the word damn in its most solemn sense (it is likely that the use of the word in Rom 13:2 also carried a lesser connotation).
The truth is that being guilty of the body and blood of Christ may not be the unpardonable sin but if it is not repented of it does expose a person to damnation (John 19:11; Heb. 10:29). We are considering here the sin of blasphemy as the Divines themselves were keen to make clear in bringing in this consideration as part of the third commandment. Careless partaking through negligent preparation or the absence of such preparation altogether fails to distinguish between common bread and the sacramental bread, which represents the Lord's body; but treats it the same which is a contempt of Christ, his ordinance and his body and blood.
This is the blood that delivers the justified from damnation (Rom. 5:9). In 1 Cor 11:32 we understand that there is a divine purpose in chastisement in order that "we should not be condemned with the world". When someone eats and drinks unworthily then chastisement is necessary to bring them to repentance otherwise they would be condemned with the world through eating and drinking damnation to themselves. Even if we were simply to understand damnation as referring to objective guilt, that guilt must be repented of and removed and "every sin deserves God’s wrath and curse". What guilt are we speaking of? The guilt of the body and blood of the Lord, i.e. the worst sin ever committed and do we not think that Paul might mean that this objective guilt is unto damnation?
Do we understand "the guilt and heinousness of this sin"? John Willison defines this as "they are guilty of the body and blood of the Lord, i.e. It is an accession to the guilt of shedding the innocent blood of our Lord and Saviour Jesus Christ. — It is an implicit approbation of the Jews' act in crucifying Christ. — It is a trampling Christ's blood under our feet. — It is a crucifying Christ afresh and harbouring the traitors and enemies of Christ in our bosom". "The sin of it is no less than murdering the Son of God, and being accessory to the guilt of shedding his innocent blood".
"It argues a low esteem and an undervaluing of Christ, his precious blood, and redeeming love...It is a solemn affront to Christ; as it is to a king to throw his picture or great seal into a puddle...It is a horrid mocking of Christ, as it is a pretense of love to him, and hatred of sin, while, in the mean time, sin is hugged and Christ despised...It is a plain accession to the guilt of the Jews and Romans, who imbrued their hands in Christ's blood; for he is reckoned accessory to a murder who consents to it, aids, or abets the murderers, and this unworthy communicants are guilty of".
"Unworthy receivers of the Lord's supper contract great guilt, and also incur great danger to themselves"."They provoke God to inflict sore judgments on them, temporal and spiritual judgments here, and eternal judgments hereafter. The meaning is not, that this sin is unpardonable, but that it deserves damnation, and will bring it on, without repentance, and flying to the blood of Christ for cleansing. Every sin is in its own nature damning, and therefore such a heinous sin, as profaning this holy ordinance, must surely be so. But timorous and fearful believers should not be discouraged from attending this holy ordinance by the sound of this word, as if they bound upon themselves the sentence of damnation, by coming to the Lord's table unprepared. For hearing and praying unworthily, incurs damnation, as well as communicating unworthily. But this sin, as well as others, leaves room for forgiveness upon repentance".
"as the virtue of this precious blood saved and cleansed many, who actually shed it at Jerusalem; so it can save and cleanse those who spill and trample it under foot in the sacrament, upon their application to it, (Luke 24:46-47; Acts 2:36,38,41; 1 John 1:7)"In relation to the word chosen by the AV translators and the Westminster Divines, I am inclined to agree with a former Professor of Church History and Principles at the Free Church College who expressed his preference for the older rendering in the face of the criticism that is all too commonly heard.
We should not lose the significance of the rendering however, as it is drawn out by Willison and "be much concerned to guard against this heinous and dangerous sin; and cry with the Psalmist, 'Lord, deliver us from blood-guiltiness.'"