This particular song is called La Promessa by Gioacchino Rossini.
The translation is as follows:
Ch'io mai vi possa lasciar d'amare, --> That I will ever be able to stop loving you
No, nol credete, pupille care, --> No, don't believe it, dear eyes!
Ne men per gioco v'ingannerò. --> Not even to joke would I deceive you about this.
Voi foste e siete le mie faville, --> You alone are my sparks,
E voi sarete, care pupille, --> and you will be, dear eyes
Il mio bel foco finch'io vivrò. --> my beautiful fire as long as I live, ah!