Negative Commandment #31
Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
Second Section – the Negative Commandments
31. It is a negative commandment "Do not swear an oath of expression falsely"
As it states in Vayikra (Leviticus) 19:12, "and you shall not swear in My Name falsely." The name for this is Shavua Betu'i (oath of expression). A person is liable to punishment for this if he swears on things that might happen, either in the past or future. Examples of statements about the past are: "that I ate" or "that I threw a stone into the water" or "that I spoke with this person about that person" or "that I did not eat" or "that I did not throw a stone into the water" or "that I did not speak with this person about that person." Examples of future events would be: "that I will eat" or "that I will not eat" or "that I will throw a rock or stone into the water" or "that I will not throw it." If a person swears on one of these things, he has transgressed this negative commandment.
This applies in all places and at all times, for men and for women.