From the opera "Griselda". Probably the most famous song from the opera is Ernesto's aria, "Per la gloria d’adorarvi", which remains to this day a popular selection for concert and recital performance (Wikipedia).
The synopsis of this opera (Wikipedia) is rather interesting:
King Gualtiero has married Griselda, a peasant woman and his longtime mistress, and fears that she will not be accepted among the nobility. Concerned that a rebellion might arise, the king decides he must prove that Griselda is worthy to be their queen and the mother of their future king. He tests her virtue and steadfastness with a series of cruel ordeals, including telling her a lie that their long-lost daughter was killed on his orders. Gualtiero banishes Griselda from the court and announces that he intends to take another wife, the young woman Almirena, who is, unknown to all, their missing daughter. Almirena is highly upset over the king's proposal as she is in love with Ernesto.
Meanwhile, Griselda has returned to the humble cottage where she once lived. A beautiful woman, she has caught the attention of Rambaldo, a Sicilian nobleman, who attempts to woo her. After refusing him, Rambaldo threatens to kill her infant son, Everardo, unless she agrees to marry him. Griselda refuses and flees to the palace where she is permitted to stay as a servant to Almirena. Gualtiero, as a final test, orders Griselda to marry Rambaldo, which she refuses to his satisfaction. The king reveals his true motive for tormenting her and accepts her again as his queen to the satisfaction of Almirena and Ernesto who can now be reunited. Rambaldo, who confesses to having stirred up the nobles in the hope of winning Griselda, is forgiven.