Oath means something declared or promised. A solemn, formal declaration or promise to fulfill a pledge, often calling on God, a god, or a sacred object as witness.

“Oath” shall include affirmation and declaration in the case of persons by law allowed to affirm or declare instead of swearing. [Section 3(36) of the General Clauses Act, 1897]

The word "oath" includes a solemn affirmation substituted by law for an oath, and any declaration required or authorized by law to be made before a public servant or to be used for the purpose of proof, whether in a Court of Justice or not. [Section 51 of the Penal Code, 1860]

All that is necessary to an oath is an appeal to the Supreme Being, as thinking him the rewarder of truth, and avenger of falsehood. [Omychund vs. Barker, 1 Atk. 21, 48, 26 Eng. Reprint. 15]

The oath of office of the Judges of the Supreme Court requires that they will preserve, protect and defend the Constitution and the laws of Bangladesh. These are not mere ornamental empty words. These glorifying words of oath eulogize the supremacy of the judiciary- Constitution of Bangladesh, 1972, Article 95. [Dr. Mohiuddin Farooque, Secretary General, Bangladesh Environmental Lawyers Association (BELA) vs. Bangladesh and others, 22 BLD (HCD) 631]

Administration of an oath to an accused person is opposed to public policy. Such administration of oath to an accused is an express statutory illegality and if oath is illegally administered to an accused, the statement made by him cannot be used as evidence. [Abdur Rashid vs. The State, (1970) 22 DLR 110]