One of the important issues in Islam is the issue of women's hijab. God says in the Quran:

O Prophet, tell the believing women to lower their gaze (from lustful looks) and guard their modesty and not display their adornment except what is apparent and to draw their veils over their chests (so that their necks and chests are covered with them)... . Surah An-Nur, verse 31

The best women are those who neither see non-mahram men nor are they seen by non-mahram men. Hazrat Zahra (peace be upon her), Bihar al-Anwar, 43/54

Question: What are the limits of Islamic hijab for women? Is it sufficient to wear long, loose clothes, trousers and a headscarf for this purpose? Basically, what quality of a woman's clothing and covering should be observed in front of non-mahram men?

Imam Khomeini (RA):

It is obligatory for a woman's entire body to be covered from a non-mahram, except for the face and hands up to the wrists, and there is no harm in wearing the aforementioned clothing if it covers the obligatory amount, but it is better to wear a veil, and clothing that attracts the attention of a non-mahram should be avoided.

Those who want to make women the playthings of men and the playthings of wicked youth are criminals. Women should not be deceived. A woman should not think that it is the position of a woman to go out in a state of disarray, with her head uncovered and naked. This is not the position of a woman. A woman should be brave. A woman is a builder of man. A woman is a teacher of man.

Hazrat Imam Khomeini (Quds-e-Sar-e), Sahifa-e-Noor, Volume 11, Page 254