Historical Background:
While many Muslims call 'hijab' an Islamic dress code, they are in fact oblivious of the fact that the concept of 'hijab' has nothing to do with Islam, nor with the Quran.
In fact, the 'hijab' is an old Jewish tradition that infiltrated the hadith books like many innovations that contaminated Islam through the hadith. Any student of Jewish traditions would know that the head cover for the Jewish woman is encouraged by the rabbis and religious leaders.
Religious Jewish women still cover their heads most of the time, especially in the synagogues, at weddings and religious festivities. This Jewish tradition is a cultural not a religious one. Hijab was observed by women of the civilisations that preceded the Jews and was passed down to the Jewish culture.
Some Christian women cover their heads on many religious occasions while the nuns cover their heads all the time. The tradition of covering the head was practiced thousands of years before Muslim scholars claimed the 'hijab' as a Muslim dress code.
The traditional Arabs, of all religions, Jews, Christians and Muslims used to wear 'hijab', not because of Islam, but because of tradition. In Saudi Arabia for example, all men cover their heads, not because of Islam but because of tradition.
North Africa is known for its Tribe (Tuareg) that have the Muslim men wearing 'hijab' instead of women. Here the tradition has the 'hijab' in reverse. If wearing 'hijab' is the sign of the pious and righteous Muslim woman, Mother Teresa would have been the first woman to be counted.
In brief, 'hijab' is a traditional dress and has nothing to do with Islam or religion. In certain areas of the world, men are the ones who wear the 'hijab' while in others the women do.
Mixing religion with tradition is a form of idol-worship since it implies setting up other sources of religious laws besides the law of God.
The word 'khimar' in the Quran:
The word 'khimar' can be found in the Quran in 24:31. While the first basic rule of Dress Code for the Muslim women can be found in 7:26, the second rule of the dress code for women can be found in 24:31. Some Muslims quote verse 31 of sura 24 as containing the 'hijab', or head cover, by pointing to the word, khumoorihinna, (their khimars), forgetting that God already used the word 'hijab', several times in the Quran, but none to mean head cover. Those who are not shackled by pre-conceptions will easily see that there is no command in 24:31 for women to cover their heads. The word 'khimar' does not mean 'hijab' nor head cover. Those who quote this verse usually add the words "head cover" or the word "veil" after the word 'khumoorihinna', usually between brackets. These additions are their own words not the words of God and they are clearly added to the text to imply a meaning not found in God's words. The words of 24:31 are:
And say to the believing women to lower their gaze and to guard their private parts and not to show their beauty spots except that of it which is normally shown. They shall also cover their cleavage with their 'khimars'. They shall not show their beauty spots except in the presence of their husbands, their fathers, the fathers of their husbands, their sons, the sons of their husbands, their brothers, the sons of their brothers, the sons of their sisters, other women, what their right hands possess, the male attendants who have no sexual desire and the children who are yet to attain awareness of women's nakedness. They shall not strike their feet so as to reveal details of their hidden beauty spots. You shall repent to God, all of you, O believers, so that you may succeed. 24:31
The Arabic word khimar means cover. Any cover can be called a khimar, such as a curtain, a dress. A table cloth that covers the top of a table is a khimar. A blanket can be called a khimar, and so on. The word 'khamr', is used in the Quran for intoxicants. It is a derivative of the word khimar. Both words mean: that which covers. The khimar covers a window, a body, a table and so on, while khamr is that which covers the mind. Traditional translators, obviously influenced by hadith and culture, claim that khimar in 24:31 has only one meaning, and that is the head cover. Thus, they mislead women into believing that 24:31 commands them to cover their hair!
In 24:31 God instructs women to use their khimar (cover/garment) to cover their cleavage. Covering the chest can be done by a dress, coat, shawl, shirt, blouse, a scarf and so on.