2,623. The First Subcategory of an Oath in Vain

Hilchos Shevuos 1:3

If someone takes an oath in one of the aforementioned four categories and acts contrary to his words, he has made a false oath. For example, if someone took an oath not to eat and he ate, or to eat and he didn’t eat, or that he ate when he didn’t, or that he didn’t eat when he did. Regarding all such cases, Leviticus 19:12 says, “Do not swear falsely in My name.” If a person intentionally swears falsely, he is liable to the penalty of lashes; if he did so unintentionally, he is liable to bring a variable guilt offering, as per Leviticus 5:4, “It was hidden from him and he didn’t know, and he became guilty.”

Hilchos Shevuos 1:4

An oath in vain also has four subcategories. #1: taking an oath about a known matter that was untrue, such as that a man was a woman, that a woman was a man, that a marble pillar was gold, and similar such things.