The 63rd prohibition is that we are forbidden from profaning G‑d's Name. This corresponds to the commandment to sanctify G‑d's Name, as we explained previously in Positive Commandment Nine.

The source of this commandment is G‑d's statement (exalted be He),1 "Do not profane My Holy Name."

This transgression has three categories: two which apply to everyone, and one which applies only to certain individuals.

The first general category [itself contains two parts: a)] when there is a decree [against Judaism], and one is pressed to transgress a commandment by someone who intends2 to make him violate the commandment — whether it is from the less serious or more serious commandments — or [b)] even when there is no decree, and one is pressed to transgress the prohibitions of idolatry or gilui arayot3 or murder. One is required to give up one's life and allow oneself to be killed rather than transgress, as explained in the Ninth Positive Commandment. If a person transgressed the prohibition rather than allowing himself to be killed, he has profaned G‑d's Name and has [thereby] transgressed this commandment. If he did so publicly, i.e. in the presence of ten Jews, he has profaned G‑d's Name in public and transgressed G‑d's commandment (exalted be He), "Do not profane My Holy Name," and his sin is very grievous.

He does not receive lashes, however, since he was forced, and the court may punish by lashes or execution only when the person transgressed intentionally, willingly, before witnesses, and after being warned. The Sifra says regarding a person who gives one4 of his children to [the idol] Molech, "The verse5 says, 'I will direct My anger against that person.' The word 'that,'6 comes to exclude one who acts unwillingly, unintentionally or mistakenly." This explains to you that one who serves idolatry because he was compelled to do so is not punished by karet, and certainly is not executed by the court. He does transgress, however, the prohibition of chillul Hashem, profaning G‑d's Name.

The second general category is when a person does a prohibited act for which he has no desire or enjoyment, but his actions show disregard and disobedience. This person also profanes G‑d's Name and is punished by lashes.7 The verse8 therefore says, "Do not swear falsely by My name; [if you do so], you will be profaning your G‑d's name," because it gives no physical pleasure, and shows disregard for this commandment.

The category which applies to certain individuals is when a person who is known for his piety and righteousness does something which seems to the public to be a sin. Since such an act is improper for such a pious man, he has profaned G‑d's Name, even though the act was permitted. As our Sages said,9 "What would be an example of profaning G‑d's Name? [Rav said,] If someone like me would take meat from the butcher without paying immediately. Another Sage said, 'If someone like me would walk four amos without learning Torah or wearing tefillin.'"

This prohibition is repeated in the verse,10 "[Do] not profane your G‑d's name; I am G‑d."

The details of this mitzvah have been explained in Pesachim11 and in the end of Yoma.12