As I said before, niqab is for SURE part of Islam as the Qu'ran commands the Prophet's wives to always observe covering their faces, even WHILE ON HAJJ (just that they were not to do so with an affixed veil but could so with whatever was available of the pilgrimage clothing).
'Aisha (RAA) said: "Pilgrims were passing by us while we were with the Prophet of Allah (saaws). When they came close to us we would draw our garments from the head to cover the face." [Abu Dawud and Ibn Majah. Ad-Daraqutni reports a similar Hadeeth on the authority of Umm Salamah (RAA). Thus, we see that covering the face was a priority of the Sahabiyat and it is certainly a characteristic of the women who opt to follow their righteous path. So at the VERY least this is the Sunnah of the prophet's wives, something approved of by the Prophet Mohammed sallalahu alahi wa salaam.
Whether it is fard (required at all times out of the home) for ALL women depends on your methodology for interpreting the evidences about jilbab [the Qu'ran commands women to wear a garment called jilbab when they leave their home]. There is some evidences to show that jilbab for many women of the Sahaba (early Muslims) did indeed cover the face. But this may have been because of this ayah (chapter) from the Holy Qu'ran: ...And when you ask [the Prophet Mohammed's wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts. And it is not [conceivable or lawful] for you to harm the Messenger of Allāh or to marry his wives after him, ever. Indeed, that would be in the sight of Allāh an enormity.(Al-Ahzāb 33:53)
Now I know this ayat is specific to the Prophet's wives, may Allah subhanhu wa ta'ala be pleased with them. Their sins were to be twice as heavy as our own, and they were forbidden to marry after their husband's death while we ordinary women are encouraged to if we wish to or are able to. But when the Prophet sallalahu allahi wa salaam came upon a woman who was not his wife (to propose marriage) there was ALREADY A COVER/PARTITION between them. Yes, this sahabiyat became his wife, but at the time she was not, and yet this was already in practice between at least this man, and this woman. The following hadith narrated by Umm Salamah:“When my ‘Iddah (This type of ‘iddah refers to the 4 months and 10 days of mourning that Allah has legislated for a woman after her husband passes away) ended from [the death of] Abi Salamah, Rasūlullah (Sallalllahu ‘Alayhi wa Sallam) came and spoke to me and between him and I was a Hijāb, and so he proposed to me…” Note, she said: "there WAS a hijab, not, "I was WEARING a hijab". What we often refer to now as hijab (the headscarf) is known in the Qu'ran specifically as a khimar. "Hijab" is an Islamic term that means "cover" such as a screen, partition, or a veil. THE WHOLE OF A MUSLIM WOMAN's MODESTY (her voice in public, her Islamic clothing, what she says, what she does) is her hijab, her portable covering. If this type of "hijab" were what the hadith were referring to, Umm Salamah would have said: "between us was Hijab", not "a hijab" which in the Arabic, grammatically refers to a specific kind of cover, [a veil, or a partition, or a screen] and not the kind that Um Salamah was wearing. You simply can not get that out of the grammer. Anyways, so maybe the Prophet sallalahu alahi wa salaam simply thought to speak to Umm Salamah (may Allah subhanahu wa ta'ala be pleased with her) from another room for propriety's sake, but stealing a comment from Revert Muslimah's post http://revertmuslimah.blogspot.com/2009/02/when-people-ask-me-about-niqab.html "another way to look at this concept would be that if in a woman's home [place of our refuge and saftety says Allah] they have [should have] a barrier or veil between her and a man why would she abandon that form of modesty when she left the home?"That is why I have always believed the niqab is mustahaab (beneficial/you get reward for wearing it) since Allah subhanhu wa ta'ala Himself has informed us in Al-Ahzāb 33:53: "That is purer for your hearts and their hearts" . If the Prophet's wives (may Allah subhanhu wa ta'ala be pleased with them) and the Sahabiyiat had less fitnah in their hearts then I do and the people who surround me, then why shouldn't I wish for an oppurtunity to have my heart be purer? Which is WHY the MAJORITY of Islamic methodology (called fiqh) says that niqab is highly recommended (a choice that God himself recommends) but that it is not obligatory---only better.
Which means the CHOICE to wear niqab IS part of our religion, and is a recommended choice from Allah subhanhu wa ta'ala. So Farhana Hassan and Tariq Fatah of the MCC (Muslim Canadian Congress) make this application to ban my rights on false grounds. Please protest. If you are a Canadian Muslims provide evidence and send it to the newpapers and your local government as well as Federal. If we have people like Farhana and Tariq standing up for our rights instead of ourselves, pretty soon we won't have any. Even if you are living abroad please write your embassy.
And yes, MCC, niqab IS a custom that predates the Qu'ran, because didn't Allah send prophets before Mohammed sallalalhu alahi wa salaam to mankind to invoke piety and righteousness and tauhid on mankind? It would have ben known to other righteous nations.
other articles I have written with evidences pertaining to niqab being a part of Islam and of strategies to defend the right to wear niqab: