A solemn appeal to God or to something holy in support of a statement.
A blasphemous use of the name of the Deity or of anything sacred.
Why should I take the oath, General Butler? – A Daughter of the Union by Lucy Foster Madison
They would not have caught us alive, you may take your oath. – Colonel Thorndyke's Secret by G. A. Henty
I could take oath to that. – The Valiants of Virginia by Hallie Erminie Rives