What is the ruling on dreams in which a man sees a foreign woman as if she were his wife? Are such dreams considered a sin? And how can he get rid of them?

If you see this woman in your dream and you do with her what you do with your wife, there is no blame upon you, because the pen is lifted from the sleeper. However, if you imagine that while awake and indulge in it, then it is not permissible, and you must divert your thoughts to prevent falling into the forbidden.