It is narrated from Hazrat Asma that I heard the Prophet (peace be upon him) say: "Any woman among you who believes in Allah and the Last Day should not raise her head from prostration until we men have raised our heads." In fact, the men's lower garments were short, so the Prophet (peace be upon him) disliked that women's gaze might fall upon the men's private parts, and at that time, people's lower garments were these sheets (they did not have trousers).