‘Amr b. Shu'aib, on his father’s authority, told that his grandfather reported the Prophet as saying, “When one of you marries his slave to his slave girl he must not look at her private parts.” A version has, “he must not look at what is below the navel and above the knee.”
Buraida reported God's Messenger as saying to ‘Ali, “Do not give a second look, ‘Ali, for while you are not to blame for the first you have no right to the second.”
Ahmad, Tirmidhi, Abu Dawud and Darimi transmitted it.
He reported the Prophet as saying, “A woman should be concealed, for when she goes out the devil looks at her.”*
* The basic idea is to lift up the eyes to look at something. Here it is explained as meaning either that the devil makes her attractive to men, or that he looks at her to seduce her and to seduce people by her.