Rossini dubbed his original version of Mose in Egitto a "tragico-sacred action"; the librettist, A.L. Tottola, combined the biblical narrative of the Exodus story with a typical love plot from a play called "L'Osiride" (Francesco Ringhieri, 1760). This peculiar combination of themes arose from Rossini's need to circumvent papal proscriptions against performances of secular opera during Lent; Tottola's creative fusion of sacred and secular elements made the resulting work a pseudo-oratorio. The dramatic themes from Exodus are treated as befits a sacred subject: choral numbers, large instrumental forces, depictions of plagues, miracles, prayers, and crowds of Egyptians and Israelites -- all very Handelian in their grandeur. The part of Moses is monumental, set for the bass voice in authoritative declamation. The operatic elements, which include a love story between a Hebrew girl and the Egyptian Prince Osiris, are treated in an entirely secular manner. Within the context of the Exodus story, the death of Osiris is retributive; he has condemned Moses to death and the Israelites must be avenged by their God; but within the love story the death of Osiris is tragic, mourned by Elcia in a tender cabaletta.
The premiere of Mose in Egitto took place on March 5, 1818, at the Teatro de San Carlo in Naples; it was extremely well received. The opening of the original version is particularly striking: the darkened stage is introduced by three ominous chords; the confused and distressed Egyptians lament the plague of darkness that has fallen over Egypt. As the Pharaoh relents and promises to allow Moses to lead the Israelites out of bondage, the chordal progression moves from minor to major, and light is restored. Haydn's Creation was one of Rossini's favorite works, and this scene was clearly inspired by Haydn's depiction of the creation of light and dark in that work. At the premiere, the opera was well received until the Red Sea crossing in the third act, during which the audience was reduced to helpless laughter at the clumsy machinery depicting the miracle. Rossini revived the opera the next year with changes to the third act; it was then that he added the famous prayer of Moses, "Dal tuo stellato soglio," or "From your starry throne."
Mose in Egitto enjoyed a second incarnation as a French opera, entitled Moise et Pharaon. This was by now traditional for the composer, who was in the habit of converting his Italian compositions for use in Paris. Mose in Egitto had already been a success on the Parisian stage both at the Theatre de l'Academie de Musique and at the Théâtre-Italien, where it was part of the standard repertory. In 1827, Rossini and two librettists, Luigi Balocchini and Etienne de Jouy, adapted the libretto, introducing a ballet in the third act, extending the work to five acts, and adding additional choral numbers. Although this French version loses some dramatic intensity, somewhat burdened under the weight of the additions, it is this version which is usually performed today.