Quote 19
OTHELLO
Behold, I have a weapon.
A better never did itself sustain
Upon a soldier's thigh. (5.2.310-312)
After Othello strangles Desdemona (for her alleged adultery) on the bed the couple shares, Othello's reference to his "weapon," which rests upon his "soldier's thigh," seems blatantly phallic, don't you think? Othello's words forge a disturbing relationship between sex and death.
Quote 20
OTHELLO
O 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 of great ones;
Prerogatived are they less than the base.
'Tis destiny unshunnable, like death.
Even then this forked plague is fated to us
When we do quicken. (3.3.309-318)
Get your highlighter out because this is important. When Othello is convinced (by Iago) that Desdemona has cheated on him, he reveals something pretty interesting about himself. It seems that Othello believes all men, both "great" and "base," are "destin[ed]" to be cuckolds. FYI: A "cuckold" is a man whose been cheated on by his wife – cuckolds are commonly associated with horns, which is why Othello refers to cuckoldry as a "forked plague" that men suffer from.
So, if Othello believes that all men are destined, from the moment of their birth, to be cheated on by their wives, then this helps to explain why Othello is so easily convinced that Desdemona has been unfaithful, despite the fact that Iago never actually shows Othello any real evidence.
Quote 21
OTHELLO
Minion, your dear lies dead,
And your unblest fate hies. Strumpet, I come.
Forth of my heart those charms, thine eyes, are
blotted.
Thy bed, lust-stained, shall with lust's blood be
spotted. (5.1.36-41)
Because Othello believes Desdemona has been cheating on him, he rationalizes (in the most irrational and disturbing way) that it's fitting for him to kill his wife on the bed they share as a married couple.