"And you shall not profane My holy name"Leviticus 22:32.

We are commanded not to desecrate G‑d's Name. This mitzvah has three applications:

a) Martyrdom: If an oppressive government arises and sets for itself the goal of eradicating Judaism and Torah, we are commanded to sacrifice our lives rather than deviate one iota from Jewish law or custom. And, at any time, we are obligated to allow ourselves to be killed rather than transgress one of the three cardinal sins—idolatry, murder, and certain forbidden sexual relations (such as adultery, incest, and homosexuality).

One who allows himself to be martyred under these circumstances has sanctified G‑d's Name. One who transgresses, has desecrated His Name.

b) Sins of Spite: One who transgresses G‑d's command not for pleasure or for the sake of perceived benefit, but simply to demonstrate indifference for G‑d's words, has desecrated G‑d's Name, having displayed open disregard for His wishes.

c) Behavior Befitting a Torah Scholar: One who is renowned for his piety may not do anything that even smells of impropriety—even if there is no transgression involved. One Talmudic rabbi said that if he were to take meat from the butcher on credit, without paying immediately, that would constitute a desecration of G‑d's Name. When a Torah scholar behaves in exemplary fashion, this causes G‑d's Name to be sanctified—and vice versa.