Why does Iago warn Otello about jealousy in Act II?

In Giuseppe Verdi’s opera Otello, Iago warns Otello to beware of jealousy in Act II as a calculated psychological tactic to manipulate him.1

After Iago plants seeds of suspicion regarding a potential affair between Desdemona and Cassio, Otello demands an explanation for Iago's earlier insinuations. Iago refuses to provide direct evidence, instead offering the warning about jealousy. By feigning reluctance and appearing to protect Otello from his own suspicions, Iago effectively deepens Otello's anxiety and forces him to confront his own insecurities. This maneuver allows Iago to appear loyal and "honest" while simultaneously ensuring that Otello begins to torture himself with doubt, making him more susceptible to Iago's subsequent fabrications and "proofs".1