There is a great deal written about making oaths and vows. The book of Kohelet says that it's far better not to make a vow than to vow and not fulfill it. The revoking of a vow needed to be done in front of a Beit Din or Jewish court. Oaths, or a שבועה, is considered even more severe and should be avoided at all costs. A שבועה from the Torah involved taking hold of a Torah scroll or Tefillin and swearing by using one of G-d's holy names. A Rabbinic oath is less severe but is something for which we are accountable. The Rambam lists various commandments in terms of their severity. He writes that violating an oath by swearing falsely, even though it is not punishable by death by the court or Karet, is still considered very severe. We must be very careful with our speech.