Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 61
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 61, with English translation by Maimonides (Rambam).
שלא לעבור על שבועת ביטוי, שנאמר "וְלֹא תִשָּׁבְעוּ בִשְׁמִי לַשָּׁקֶר" (ויקרא יט, יב)
Not to violate an oath, as [Leviticus 19:12] states: "Do not swear falsely in My name."