I hate the Moor:
And it is thought abroad, that ‘twixt my sheets
He has done my office. I know not if ‘t be true,
But I, for mere suspicion in that kind,
Will do as if for surety.

– William Shakespeare

Othello, Act 1, Scene 3. Iago has heard rumors that his wife Emilia has slept with Othello. This gives him the additional motivation to want to destroy Othello, who he hates and is intensely jealous of. However, there is no evidence that Emilia has been unfaithful to Iago. But Iago is by nature an insecure, bitter and suspicious person. In this soliloquy he admits to not knowing if the rumors are true, but intends to act as if they are and punish Othello anyway. Iago uses a metaphor to let us know what it is said Othello has been up to with Emilia – "’twixt my sheets He has done my office."