Othello's jealousy over his wife's supposed adulterous affair with his newly appointed lieutenant, Michael Cassio, is evident in many excerpts from the play. They often appear in his scenes with the manipulative Iago, who is consistently trying to convince Othello of his wife's infidelity. One of the most poignant examples of Othello's jealousy is his soliloquy following a conversation with Iago, in which Iago claims to have knowledge of Desdemona's unfaithfulness, and uses her unfaithfulness to her father when marrying Othello as an example. Othello laments, in act 3, scene 3, lines 265-283:
If I do prove her haggard,
Though that her jesses were my dear heartstrings,
I’d whistle her off and let her down the wind
To prey at fortune. Haply, for I am black
And have not those soft parts of conversation
That chamberers have, or for I am declined
Into the vale of years—yet that’s not much—
She’s gone, I am abused, and my relief
Must be to loathe her. Oh, curse of marriage
That we can call these delicate creatures ours
And not their appetites! I had rather be a toad
And live upon the vapor of a dungeon
Than keep a corner in the thing I love
For others' uses. Yet ’tis the plague to great ones,
Prerogatived are they less than the base.
'Tis destiny unshunnable, like death.
Even then this forkèd plague is fated to us
When we do quicken.
Here, Othello claims that marriage is an awful thing because it allows for brief happiness with a beautiful woman but doesn't restrain the woman's desires, while also making excuses for her indiscretion by using the reasons of his race and lack of cordiality. In his mind, his betrayal by Desdemona is expected but still painful.