The Messenger of Allah (sal Allahu alaihi wa sallam) said: “A man who thinks about the body of a woman under her clothes until he can visualize her shape, will not even smell the fragrance of Paradise.” [Albahr-ul Raaiq, vol. 8, p. 218]
A woman who keeps herself hidden and covered would hate to be the object of a strange man’s fantasies. There is no police in the world that can know or prevent a man from thinking about another woman. The only person who can stop him is himself. The only police that he can be scared of, are Allah’s angels who will carry out His orders of punishment, since nothing remains hidden from Him.
You are your own police. Let your conscience police you before Allah’s angels have to do the job! Thinking about and imagining the looks of a non-Mahram is forbidden in the Shariah. So save yourself from unworthy thoughts – thoughts that will keep you out of Paradise!