Why does Otello demand that Desdemona produce the handkerchief in Act III?

In Giuseppe Verdi’s opera Otello, the titular character demands that Desdemona produce the handkerchief in Act III because he has been manipulated by Iago into believing that she has committed adultery with Cassio.1

Otello views the handkerchief—a gift he originally gave to Desdemona—as a symbol of their bond and fidelity. Having been convinced by Iago that Desdemona gave this token to Cassio as a sign of love, Otello uses the item as a test of her honesty. When she is unable to produce it, he interprets her failure as definitive proof of her unchastity and betrayal. This confrontation serves as a pivotal moment in the opera, fueling Otello’s descent into a murderous, jealous rage as he becomes convinced of his wife's infidelity.1