Allah said,

(And from these (angels) people learn that by which they cause separation between man and his wife,) This means, "The people learned magic from Harut and Marut and indulged in evil acts that included separating spouses, even though spouses are close to, and intimately associate with each other. This is the devil's work.'' Muslim recorded that Jabir bin `Abdullah said that the Messenger of Allah said,

(Satan erects his throne on water and sends his emissaries among the people. The closest person to him is the person who causes the most Fitnah. One of them (a devil) would come to him and would say, `I kept inciting so-and-so, until he said such and such words.' Iblis says, `No, by Allah, you have not done much.' Another devil would come to him and would say, `I kept inciting so-and-so, until I separated between him and his wife.' Satan would draw him closer and embrace him, saying, `Yes, you did well.')

Separation between a man and his wife occurs here because each spouse imagines that the other spouse is ugly or ill-mannered, etc.