Il Giuramento

Il giuramento (The Oath) is an opera in three acts by the Italian composer Saverio Mercadante. The libretto, by Gaetano Rossi, is based on Victor Hugo's play Angélo, tyran de Padoue. (This is the same source as Arrigo Boito, under the pseudonym of Tobia Gorrio, was to use for his libretto for Ponchielli's La Gioconda).
The opera was first performed at La Scala, Milan on 11 March 1837 and was "quickly taken up by other theatres throughout Italy". Within a year, it was staged in Vienna (April 1838) and later appeared in many European cities including London (June 1840) and Paris (1858) and in New York (February 1848).