The
62nd prohibition is that we are forbidden to swear a sh'vuas shav (a vain oath).
The
source of this commandment is G‑d's statement, "Do not take the name of G‑d your L‑rd in
vain."
[A
sh'vuas shav is] when one swears that
something is the opposite of what it actually is; or that something exists, when in fact it
cannot; or that he will violate a mitzvah of the Torah. So too if one swears to an obvious and
undisputed fact, such as swearing to G‑d that anything which is slaughtered
will die. This is also considered a sh'vuas
shav.
The
Mishneh says, "What is a sh'vuas
shav? An oath which contradicts an obvious truth."
One
who transgresses this prohibition intentionally is punished by lashes. If done
unintentionally, he is exempt [from even bringing a sacrifice], as with many
other prohibitions, as explained above.
There
— i.e. in tractate Sh'vuos — it is said that this is the sh'vuas shav for which one is lashed if done intentionally and
exempt if done unintentionally. The details of this mitzvah are explained there.