Ironically, Iago doesn’t have to prove his own fidelity to Othello for Othello to take everything Iago suggests on faith. On the contrary, Othello actually infers that Iago holds back more damning knowledge of Desdemona’s offenses out of his great love for Othello. Again and again, Iago insists that he speaks out only because of this love. His claim, “My lord, you know I love you” (III.iii.121) even echoes Peter’s insistent words to Christ, “Lord, thou knowest that I love thee” (John 21:15–17).
Othello’s rejection of Desdemona’s offer of her handkerchief is an emphatic rejection of Desdemona herself. He tells her he has a pain “upon” his forehead and dismisses her handkerchief as “too little” to bind his head with, implying that invisible horns are growing out of his head. Horns are the traditional symbol of the cuckold, a husband whose wife is unfaithful to him. Othello’s indirect allusion to these horns suggests that the thought of being a cuckold causes him pain but that he is not willing to confront his wife directly with his suspicions.
The end of Act III, scene iii, is the climax of Othello. Convinced of his wife’s corruption, Othello makes a sacred oath never to change his mind about her or to soften his feelings toward her until he enacts a violent revenge. At this point, Othello is fixed in his course, and the disastrous ending of the play is unavoidable. Othello engages Iago in a perverse marriage ceremony, in which each kneels and solemnly pledges to the other to take vengeance on Desdemona and Cassio. Just as the play replaces the security of peace with the anxiety of domestic strife, Othello replaces the security of his marriage with the hateful paranoia of an alliance with Iago. Iago’s final words in this scene chillingly mock the language of love and marriage: “I am your own forever” (III.iii.482).