Peter Shaffer’s Amadeus is animated by a biblical intertext which establishes a dialogic encounter between the modern play and a biblical chain of tales. Underlying the dramatic conflict between Salieri, the bitterly jealous, mediocre composer and Amadeus, the brilliant musician of immortal fame, is the drama of Saul, the hapless first King of Israel, and David, his charismatic successor, as narrated in 1 Samuel. The biblical prototype planted in Shaffer’s play pulls us back in time to a mythic past even as we sink into the depths of Salieri’s subconscious, and the play as a whole into the zone of hallucinations and nightmares. Salieri, the powerful Kapellmeister who descends into madness and obsessively plans to destroy the more gifted newcomer, recalls King Saul, tortured by the “evil spirit” and relentlessly pursuing young David. The biblical intertext in this play is studied in light of traditional theories of the intertextual activity as a deliberate authorial strategy as well as postmodern theories that view every text as a galaxy of past texts and remove the author’s intention from consideration. Michael Riffaterre’s theory of the intertextual fragments as the ”unconscious” of the text is helpful in understanding the function of the biblical patterns buried in Shaffer’s play. This paper further studies the discursive energy between the biblical intertext and Amadeus, illustrating how the past text illuminates the modern drama, while at the same time the latter may shed a new light on the lacunas in the terse biblical prose.