The Treatise on Rights by Imam Zain al Abidin (A.S) Rights of Allah -5

5. Rights of Sight

"The right of sight is that you lower it before everything which is unlawful to you and that you take heed whenever you look at anything." The eye has rights against man. 

Among them is that he should prevent it from looking at what Allah has prohibited as well as he should use it in useful things such as knowledge, that he may with it educate himself and profit his society.