An answer to the said question is as under:

1. Generally speaking, it is a very good of a person to despise and abhor immodesty and sins from the core of his heart. Immodesty of women is not only a sin by itself but it also leads others to sins. The girls' wearing immodest dress, however, does not become a license for people to look at them with the intention of seeking sexual pleasure. In fact, every mature and sane individual is answerable to his own deeds because he has been created free; he can control himself and avoid sinning despite having the chances of sinning. Many faithful people specially the youth come across such sinful scenes but they guard themselves and do not commit any sins.

2. Every sin entails special negative effects. Casting lustful look at non-mahram women have negative impacts on man's individual and social life. We shall point out some examples of those impacts as below:

Imam Ali (a) says: "Whoever lets his eye free, always has an uneasy temper."[i]

Imam Sadiq (a) also says in this regard, "Looking at a non-mahram is one of the poisonous arrows of the Satan; it is a look that may lead to a long regret."[ii]

Also, the Imam said: "Continuous look (at a non-mahram) will sow the seed of lust in the heart and it will be sufficient for the destruction of the looker."[iii]

3. If a person has been looking at non-mahram women with the intention of seeking pleasure and he has not repented, it is possible that he might continue looking at non-mahram women even after marriage, and it might increase, and its effects on the relationship between him and his wife are undeniable. It might lead to differences, separation and divorce.

For further details, see the following indexes:

-          Sins and their Effects; question 204 (site: 1073)

-          Islam and Healthy Boy-Girl Relationship; question 1044 (site: 1110)

-          Co-Education in Universities; question 4969 (site:5225)

-          The Law of Hijab and the Reason behind its Mandatoriness; question 1174 (site:1177)

-          Also for further information about the evil consequences of looking at non-mahram women, go to Hawzah.net.