Islam encourages both men and women to try as much as possible to lower their gaze, and protect their sight from unlawful things including looking at women with bad intentions. The question now is, what if the woman is very well covered up with Hijab, is it then permissible for men to feel at ease and enjoy the sight?
Well, there is no harm in looking at a woman who is Islamically well dressed. However, it depends on the type of garment and also the intention of the man in question. That is to say, if looking at the woman’s clothes brings lust in the man, then it is haram to look at her because looking lustfully is definitely a sin which is clearly stated in the Holy Quran:
Tell the believing men to lower their gaze, and protect their private parts. That is purer for them. Verily, Allah is All-Aware of what they do.
As for the Holiest Prophet of Allah, he warned against sitting on the street due to the temptation of looking at unlawful things. He told the companions to beware of sitting on the street but they said they have no other alternative than to sit there and converse with one another. The prophet then said to them that if they must sit there then they have to give the street its rights which include:
lowering gaze, returning greetings of Salaam and enjoining what is good and forbidding what is evil. (Sahih)
If a non-Mahram woman dress with very thick clothes which totally covers her as expected of her, then there is no harm for a man to look at her. However, he would be looking only at her clothes and not her body. This is permissible only if her clothes are not tight, if they are too tight that it reveals her body shapes, like tight trousers that reveal all the shape of her thighs and shins, then looking at her can arouse lust in the man which is not permissible.
Similarly, some women dress with thin clothes like those thin see-through muslim-made hijab that reveals the hair, the blackness of their hair, their ears or necks. Others too wear very thin see-through outfits or shirts which have small spaces in between, which completely reveal their stomachs and backs; looking at women in any of these states is considered haram and it is also haram for women to wear such clothes in such situations.