What might be some reasons to ask to stop reviewing an article by the editor? Recently I have been asked by a journal to review an article as a referee. I did it within 3 days, and the very next day another mail came asking me to review another article. I was reviewing it when, aft after 2 days, the editor sent me an email saying I don't need to review it anymore. What might be the reasons behind this?
There are many possible reasons. Perhaps the author(s) withdrew it. Perhaps the editor made a decision somehow, though given the time, probably a reject.
Of course, you can ask the editor, and you may or may not get a real reason.