Definition - What does Oath mean?
An oath is a confirmation that a person takes or agrees to that binds them to be honest about any particular situation or to act honestly within a role. A common oath is when a witness takes the stand in a court case; they are required to swear an oath to tell the truth, the whole truth, and nothing but the truth. Most oaths have a religious bearing as well, including the oath witnesses have to take, as the words 'so help me God' are included within the oath. An oath taken within a job includes an oath of public office that any government official would take which binds the official to their own words that they agreed to do (or not to do) a particular function or act.
Justipedia explains Oath
There are times that witnesses in court cases object to being bound by the normal oath because it involves the use of the Bible while being asked to place a hand on it while reciting the oath. At times when a witness objects to taking this oath as given, a comparable book or reference will be used. A common example is the replacement of the Bible with the Koran and the word God with Allah.