1. Blasphemy is the act of cursing the Creator. It is a deed so indescribably heinous that the Talmud, whenever referring to blasphemy, calls it by the euphemistic term "blessing God," to avoid directly expressing the idea of cursing God, the Father of all.
3. Blasphemy falls into the category of revenge. When someone is harmed by a person and seeks revenge, he may shout at the person or curse him. If the harm is great, the one seeking vengeance may not be satisfied by words alone but may physically strike out at the one who harmed him. In extreme cases, the vengeful person may not be satisfied till he kills. This is between a man and his neighbor. Between man and God it is somewhat different. Man cannot kill God nor can he strike Him physically. The ultimate revenge that man can take against God is to curse Him. Therefore, blasphemy is seen as the expression of the desire to hurt God, even to erase His existence or murder Him.
4. The prohibition against blasphemy comes to teach us not to speak evil against God nor to detract from His exaltedness in any way by intentionally using words to lessen the reverence and faith that are due Him.
5. As with any of the Seven Universal Commandments, before one can be tried in a court of law for having transgressed a commandment, there must be a witness to the deed who is willing to testify against the accused. This poses a problem, for how can the witness testify against the accused unless he repeats the blasphemous expression used, which would be a further transgression of this commandment?
6. In the Jewish courts of law, the matter was handled in the following manner. The witnesses during the entirety of the trial were directed to use a euphemistic phrase for the actual blasphemous utterance that they heard, eliminating reference to God in the phrase. Then, at the conclusion of the proceedings, the courtroom was cleared of all but those essential to the trial, and the witnesses were obliged to repeat the actual blasphemy that they heard. Upon hearing the blasphemy, the judges rent their garments as one does for the death of a parent or any other tragedy that elicits grief.
7. Rabbi Chiya declared that after the destruction of the Second Temple, one who heard blasphemy was no longer required to rend his garments, otherwise all would be walking around with their garments in tatters.
8. The Code of Jewish Law, which is the final word in determining the religious obligations of the Jew, states that a person who hears blasphemy is commanded to place the blasphemer under a ban of excommunication, regardless of whether the blasphemy was uttered against God's Name or any of His Divine attributes, whether in the Hebrew language or any of the other languages of the world, or whether the blasphemer was a Jew or a Gentile. This ban of excommunication means that the person has no rights as a member of the community and that all are forbidden to speak to him.
9. Profaning the Lord of Hosts with one's lips, God forbid, is a transgression similar to, but worse than, idolatry. Whereas idolatry is the act of worshiping a creation and thereby denying the true existence of the Creator, blasphemy is an acknowledgment of His existence but a denial of His greatness or His goodness. The blasphemer denies the truth that everything comes directly from God solely for mankind's benefit and as a bestowal of goodness. Often the goodness is unrevealed, as with a person's pain and suffering. At these times, one with a coarse consciousness or without a sufficient degree of faith in God can come to verbally express dissatisfaction with his lot through blasphemy, and thus transgress the law.
10. We see the essence of this problem in the Book of Job. Job, God's faithful servant, was struck by Satan with boils from the soles of his feet to the crown of his head. As he sat in agony from the affliction, his wife scolded him, saying, "Are you still holding fast to your integrity? Curse God, and die." But he answered her, "You speak as one who is despicable. Should we accept only the good from God and not also accept the evil? With all this, Job did not sin with his lips" (Job 2:9‑10).
11. Consistent with this, it is a Jewish tradition to bless God for the bad as well as for the good. Even when, God forbid, one hears news of a person's death, he responds by saying, Baruch Dayan Emet (Blessed be the True Judge).
12. Blasphemy as an expression of an incomplete faith in God is epitomized by the false notion that there are two powers and two kingdoms, God's and Satan's. All such theology denies that God is the Lord and Master of all.
13. The Book of Job shows clearly that God is the Ruler of Satan as well as of everyone and everything else, for when Satan wishes to test Job, he first petitions God for permission, whereby God sets definite boundaries for Satan, commanding him not to take Job's life, saying, "Behold, he is in thy hand, but guard his life" (Job 2:6).
14. The teaching in Christian theology that the evil force rebelled against the Lord and set up a separate kingdom is tantamount to blasphemy, for it denigrates the Creator and denies His infinite majesty.
15. Some authorities state that false oaths or meaningless oaths whereby one invokes the Name of God are forbidden under the category of blasphemy. An example of a false oath would be for one to take an oath in God's Name that a tree is a rock, and a meaningless oath would be for one to swear in God's Name that a tree is a tree. There is a difference of opinion as to whether one who delays fulfilling an oath violates the law.
Transgressing the prohibition of blasphemy; piety
1. The prohibition of blasphemy is transgressed even if one uses another term for God, for example, an attribute or epithet such as the Merciful One, the Father, or any other descriptive term. No matter how one curses God, and no matter in what language, the one who transgresses this commandment is subject to the death penalty by a court of law.
2. If anyone acknowledges that an idolatry is true, even though he does not serve it, it is as if he reviles and blasphemes the mighty and exalted Name of God. Whether a person is an idolater or a blasphemer, it is the same in that both deny God.
3. One who blasphemes and instantly retracts his words is nonetheless guilty if he blasphemed in front of witnesses. If he blasphemes in private and his words are heard by no one other than himself and his Creator, let him repent and God will forgive his transgression.
4. One who curses God in the name of idolatry is subject to being attacked and killed by zealots, who are, in turn, held harmless by the law. But one who is not a zealot, but seeks reprisal against a transgressor because of a desire for justice, must begin proceedings through due process of law against the accused.
(Note: A zealot is one who serves God with a selfless, passionate love and is jealous for God's honor. Reacting to a desecration of God's Name, the zealot takes immediate action to stop the desecration. If one has to ponder the situation or ask the opinion of another, wiser than he in such matters, his hesitation or intellectual inquiry takes him out of the category of the zealot, and he is forbidden to take action. The scriptural source for the action of a zealot is seen in the heroics of Phineas, who stopped a plague among the Children of Israel when he slew a prince of the tribe of Simeon and the Midianite woman with whom he was having forbidden sexual relations (Num. 25:7‑8).
5. It should be the goal of every one of the Children of Noah to strive to do more than the minimum that the law requires, for this is the idea of piety, and one who accepts the responsibility of fulfilling the Seven Laws of Noah is called one of the pious of the nations. Bearing this in mind, a person is well advised to withhold speaking evil about his fellow man as well as against his Creator, for in God's image was man created, and one who reviles his fellow insults God as well. If, by words alone, one destroys a favorable picture of a person in another's mind, this is considered killing him. And it matters not whether the destructive words are true or false.
6. Striving to go beyond, the letter of the law has no limit, for the commandments of God are as deep as the ocean and as wide as the sky. Since everything in creation reflects the hand of the Creator, a truly pious person withholds himself from speaking negatively against anything. There are times, however, when it is appropriate and even mandatory to speak out against someone. For instance, when someone is engaged in wicked pursuits and it appears that others will follow his lead, then it becomes a great kindness and even an obligation to speak in condemnation of the transgressor. But in the main, gossip, calumny, and tale‑bearing, even when the statements are true, will stand in the way of the individual's spiritual and moral growth.
 Sefer Hahinnukh, Commandment 70
 Mishnah Sanhedrin, 7:5
 Babylonian Talmud, Sanhedrin 60a
 Shulchan Arukh, Yoreh Deah, 340, law 37
 Book of Commandments, Rambam (Maimonides), Negative Commandment 317
 Mishnah Brachot. 9:5
 Ibid., 9:2; Shulchan Arukh, Orach Chaim, chapter 222, law 2
 Mishneh Torah, Laws of Kings, chapter 10, law 7, Mishneh l'Melech, "Isaw..."
 Jerusalem Talmud, Nazir, chapter 9, law 1, Pnei Moshe, "Israel should not delay..."
 Mishneh Torah, Laws of Kings, chapter 9, law 3
 Ibid., Laws of Idolatry, chapter 2, law 6
 Ibid., law 9
 Job 11:9
 Horev, Rabbi S. R. Hirsch, chapter 90, notes 582‑584
 Ibid., chapter 53, notes 386‑392