Short answer
Yes, it is a serious sin. Covering in front of non-mahram men is fard, and many scholars count openly leaving it among the major sins because of the hadith about women who are clothed yet naked. The Quran sets no worldly punishment for it, and no one may punish a woman for it. Sincere repentance wipes it out.
Leaving the fard covering of the awrah in front of non-mahram men is sinful, and doing so openly and habitually is treated by Hanafi muftis as a major sin (kabirah). It does not make a woman a disbeliever while she accepts that hijab is Allah's command, and sincere tawbah (repentance) removes it.
The four schools agree on this.
Explanation
Hijab is not a cultural extra. Allah commands believing women to draw their head covers over their chests and not to show their adornment except to close family, and He says that when Allah and His Messenger have decided a matter, a believer has no other choice in it. So leaving hijab means leaving a clear command, and the four schools agree it is sinful.
Why many call it a major sin. Scholars describe a major sin as one that carries a specific threat in the Hereafter. The Prophet ﷺ described women who are clothed yet naked and said they will not enter Paradise or smell its fragrance. Ahl al-Sunnah read such warnings as what the deed deserves: a believer does not stay in the Fire forever, and Allah may forgive her altogether. Doing a sin openly and repeatedly also makes it weightier.
What the Quran does not say. No verse sets a worldly penalty for not wearing hijab, and no hadith tells families or strangers to punish a woman for it. Harshness, insults and force are not the sunnah. Advice should be private, gentle and patient. See is it haram to force hijab.
If you have taken it off:
- You are still a Muslim. See is a woman who does not wear hijab still Muslim.
- Your other deeds still count. Keep praying and fasting.
- Repent: regret it, intend to return to it, and ask Allah for help. He forgives the one who turns back.
- Small steps count. Covering more today than yesterday is good.
If hijab feels hard because of family, work or fear, see taking off hijab for work or safety and the hijab guide.
The evidence
Quran, Surah An-Noor 24:31
وَقُل لِّلْمُؤْمِنَٰتِ يَغْضُضْنَ مِنْ أَبْصَٰرِهِنَّ وَيَحْفَظْنَ فُرُوجَهُنَّ وَلَا يُبْدِينَ زِينَتَهُنَّ إِلَّا مَا ظَهَرَ مِنْهَا ۖ وَلْيَضْرِبْنَ بِخُمُرِهِنَّ عَلَىٰ جُيُوبِهِنَّ ۖ وَلَا يُبْدِينَ زِينَتَهُنَّ إِلَّا لِبُعُولَتِهِنَّ أَوْ ءَابَآئِهِنَّ أَوْ ءَابَآءِ بُعُولَتِهِنَّ أَوْ أَبْنَآئِهِنَّ أَوْ أَبْنَآءِ بُعُولَتِهِنَّ أَوْ إِخْوَٰنِهِنَّ أَوْ بَنِىٓ إِخْوَٰنِهِنَّ أَوْ بَنِىٓ أَخَوَٰتِهِنَّ أَوْ نِسَآئِهِنَّ أَوْ مَا مَلَكَتْ أَيْمَٰنُهُنَّ أَوِ ٱلتَّٰبِعِينَ غَيْرِ أُو۟لِى ٱلْإِرْبَةِ مِنَ ٱلرِّجَالِ أَوِ ٱلطِّفْلِ ٱلَّذِينَ لَمْ يَظْهَرُوا۟ عَلَىٰ عَوْرَٰتِ ٱلنِّسَآءِ ۖ وَلَا يَضْرِبْنَ بِأَرْجُلِهِنَّ لِيُعْلَمَ مَا يُخْفِينَ مِن زِينَتِهِنَّ ۚ وَتُوبُوٓا۟ إِلَى ٱللَّهِ جَمِيعًا أَيُّهَ ٱلْمُؤْمِنُونَ لَعَلَّكُمْ تُفْلِحُونَ ﴿٣١﴾
And tell the believing women to reduce [some] of their vision and guard their private parts and not expose their adornment except that which [necessarily] appears thereof and to wrap [a portion of] their headcovers over their chests and not expose their adornment except to their husbands, their fathers, their husbands' fathers, their sons, their husbands' sons, their brothers, their brothers' sons, their sisters' sons, their women, that which their right hands possess, or those male attendants having no physical desire, or children who are not yet aware of the private aspects of women. And let them not stamp their feet to make known what they conceal of their adornment. And turn to Allah in repentance, all of you, O believers, that you might succeed.
Commands believing women to draw their head covers over their chests and not to show their adornment except to close family.
Quran, Surah Al-Ahzaab 33:36
وَمَا كَانَ لِمُؤْمِنٍۢ وَلَا مُؤْمِنَةٍ إِذَا قَضَى ٱللَّهُ وَرَسُولُهُۥٓ أَمْرًا أَن يَكُونَ لَهُمُ ٱلْخِيَرَةُ مِنْ أَمْرِهِمْ ۗ وَمَن يَعْصِ ٱللَّهَ وَرَسُولَهُۥ فَقَدْ ضَلَّ ضَلَٰلًۭا مُّبِينًۭا ﴿٣٦﴾
It is not for a believing man or a believing woman, when Allah and His Messenger have decided a matter, that they should [thereafter] have any choice about their affair. And whoever disobeys Allah and His Messenger has certainly strayed into clear error.
A believer does not set aside a clear command of Allah and His Messenger.
Sahih Muslim 2128
Sahih... لا يدخلن الجنة ولا يجدن ريحها ...
"They will not enter Paradise, nor will they find its fragrance."
This warning about women who are clothed yet naked is why many scholars class open unveiling as a major sin.
Where the ruling is recorded
- al-Hidaya, Kitab al-Karahiyya, chapter on looking and touching. A free woman's whole body is awrah before non-mahram men except the face and hands.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, chapter on the conditions of prayer, covering the awrah. Defines the awrah of a woman, which must be covered.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.