Short answer
Two. In the Hanafi school they can be two Muslim men, or one Muslim man and two Muslim women, who are sane, adult and hear the offer and acceptance together. The Shafi'i and Hanbali schools accept only two just Muslim men. Without witnesses the nikah is not valid.
Two witnesses are a condition of validity: two Muslim men, or one Muslim man and two Muslim women, all sane, adult and free, who hear and understand the ijab and qabul in the same sitting. Their being of good character is preferred, but a nikah witnessed by ordinary Muslims of weak practice is still valid.
Other madhhabs
- Shafi'i
- Two Muslim men who are just ('adl). Women's witness does not count for nikah.
- Maliki
- Two just men are required, but their presence is needed before consummation rather than at the contract itself. Public announcement is also stressed.
- Hanbali
- Two just Muslim men. A nikah witnessed only by women is not valid.
Explanation
Witnesses are what turn a private promise into a public marriage. They protect the woman's rights, the lineage of children and the couple's reputation. This is why every school requires witnesses in some form, and why a "nikah" between two people alone, with Allah as the only witness, is not a marriage.
What the Hanafi school asks of the witnesses:
- They are Muslim, sane and adult. Children and non-Muslims do not count when the bride is Muslim.
- Two men, or one man and two women. Four women without a man are not enough.
- Both witnesses hear the offer and the acceptance at the same time and understand that a nikah is being made. If one hears the offer today and the other hears the acceptance tomorrow, it does not count.
- The bride's father or brother can be a witness, and so can the groom's relatives.
The wali and the imam are not counted as extra witnesses unless they are acting as witnesses. If a father contracts his adult daughter's nikah with her permission while she is present, the Hanafi books count the father and one other man as the two witnesses. Choosing practising, trustworthy witnesses is better, and it keeps the nikah valid by the stricter conditions of the other schools. For a nikah where one side is overseas, see online nikah. The full list of conditions is in conditions of a valid nikah.
The evidence
Quran, Surah An-Nisaa 4:25
وَمَن لَّمْ يَسْتَطِعْ مِنكُمْ طَوْلًا أَن يَنكِحَ ٱلْمُحْصَنَٰتِ ٱلْمُؤْمِنَٰتِ فَمِن مَّا مَلَكَتْ أَيْمَٰنُكُم مِّن فَتَيَٰتِكُمُ ٱلْمُؤْمِنَٰتِ ۚ وَٱللَّهُ أَعْلَمُ بِإِيمَٰنِكُم ۚ بَعْضُكُم مِّنۢ بَعْضٍۢ ۚ فَٱنكِحُوهُنَّ بِإِذْنِ أَهْلِهِنَّ وَءَاتُوهُنَّ أُجُورَهُنَّ بِٱلْمَعْرُوفِ مُحْصَنَٰتٍ غَيْرَ مُسَٰفِحَٰتٍۢ وَلَا مُتَّخِذَٰتِ أَخْدَانٍۢ ۚ فَإِذَآ أُحْصِنَّ فَإِنْ أَتَيْنَ بِفَٰحِشَةٍۢ فَعَلَيْهِنَّ نِصْفُ مَا عَلَى ٱلْمُحْصَنَٰتِ مِنَ ٱلْعَذَابِ ۚ ذَٰلِكَ لِمَنْ خَشِىَ ٱلْعَنَتَ مِنكُمْ ۚ وَأَن تَصْبِرُوا۟ خَيْرٌۭ لَّكُمْ ۗ وَٱللَّهُ غَفُورٌۭ رَّحِيمٌۭ ﴿٢٥﴾
And whoever among you cannot [find] the means to marry free, believing women, then [he may marry] from those whom your right hands possess of believing slave girls. And Allah is most knowing about your faith. You [believers] are of one another. So marry them with the permission of their people and give them their due compensation according to what is acceptable. [They should be] chaste, neither [of] those who commit unlawful intercourse randomly nor those who take [secret] lovers. But once they are sheltered in marriage, if they should commit adultery, then for them is half the punishment for free [unmarried] women. This [allowance] is for him among you who fears sin, but to be patient is better for you. And Allah is Forgiving and Merciful.
Marriage is set apart from secret relationships, and witnesses are what make it known.
Quran, Surah Al-Baqara 2:282
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِذَا تَدَايَنتُم بِدَيْنٍ إِلَىٰٓ أَجَلٍۢ مُّسَمًّۭى فَٱكْتُبُوهُ ۚ وَلْيَكْتُب بَّيْنَكُمْ كَاتِبٌۢ بِٱلْعَدْلِ ۚ وَلَا يَأْبَ كَاتِبٌ أَن يَكْتُبَ كَمَا عَلَّمَهُ ٱللَّهُ ۚ فَلْيَكْتُبْ وَلْيُمْلِلِ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ وَلْيَتَّقِ ٱللَّهَ رَبَّهُۥ وَلَا يَبْخَسْ مِنْهُ شَيْـًۭٔا ۚ فَإِن كَانَ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ سَفِيهًا أَوْ ضَعِيفًا أَوْ لَا يَسْتَطِيعُ أَن يُمِلَّ هُوَ فَلْيُمْلِلْ وَلِيُّهُۥ بِٱلْعَدْلِ ۚ وَٱسْتَشْهِدُوا۟ شَهِيدَيْنِ مِن رِّجَالِكُمْ ۖ فَإِن لَّمْ يَكُونَا رَجُلَيْنِ فَرَجُلٌۭ وَٱمْرَأَتَانِ مِمَّن تَرْضَوْنَ مِنَ ٱلشُّهَدَآءِ أَن تَضِلَّ إِحْدَىٰهُمَا فَتُذَكِّرَ إِحْدَىٰهُمَا ٱلْأُخْرَىٰ ۚ وَلَا يَأْبَ ٱلشُّهَدَآءُ إِذَا مَا دُعُوا۟ ۚ وَلَا تَسْـَٔمُوٓا۟ أَن تَكْتُبُوهُ صَغِيرًا أَوْ كَبِيرًا إِلَىٰٓ أَجَلِهِۦ ۚ ذَٰلِكُمْ أَقْسَطُ عِندَ ٱللَّهِ وَأَقْوَمُ لِلشَّهَٰدَةِ وَأَدْنَىٰٓ أَلَّا تَرْتَابُوٓا۟ ۖ إِلَّآ أَن تَكُونَ تِجَٰرَةً حَاضِرَةًۭ تُدِيرُونَهَا بَيْنَكُمْ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَلَّا تَكْتُبُوهَا ۗ وَأَشْهِدُوٓا۟ إِذَا تَبَايَعْتُمْ ۚ وَلَا يُضَآرَّ كَاتِبٌۭ وَلَا شَهِيدٌۭ ۚ وَإِن تَفْعَلُوا۟ فَإِنَّهُۥ فُسُوقٌۢ بِكُمْ ۗ وَٱتَّقُوا۟ ٱللَّهَ ۖ وَيُعَلِّمُكُمُ ٱللَّهُ ۗ وَٱللَّهُ بِكُلِّ شَىْءٍ عَلِيمٌۭ ﴿٢٨٢﴾
O you who have believed, when you contract a debt for a specified term, write it down. And let a scribe write [it] between you in justice. Let no scribe refuse to write as Allah has taught him. So let him write and let the one who has the obligation dictate. And let him fear Allah, his Lord, and not leave anything out of it. But if the one who has the obligation is of limited understanding or weak or unable to dictate himself, then let his guardian dictate in justice. And bring to witness two witnesses from among your men. And if there are not two men [available], then a man and two women from those whom you accept as witnesses - so that if one of the women errs, then the other can remind her. And let not the witnesses refuse when they are called upon. And do not be [too] weary to write it, whether it is small or large, for its [specified] term. That is more just in the sight of Allah and stronger as evidence and more likely to prevent doubt between you, except when it is an immediate transaction which you conduct among yourselves. For [then] there is no blame upon you if you do not write it. And take witnesses when you conclude a contract. Let no scribe be harmed or any witness. For if you do so, indeed, it is [grave] disobedience in you. And fear Allah. And Allah teaches you. And Allah is Knowing of all things.
The general Quranic pattern of two men or one man and two women, which the Hanafis apply to nikah.
Sunan an-Nasa'i 3369
Graded hasan... فصل ما بين الحلال والحرام الدف والصوت ...
"What separates the lawful from the unlawful is the daff and the voice."
A lawful marriage is one that is made known, not hidden.
Where the ruling is recorded
- al-Hidaya, Kitab al-Nikah, opening chapter on witnesses. Nikah is not concluded without two free, sane, adult Muslim witnesses, or one man and two women.
- al-Fatawa al-Hindiyya, Kitab al-Nikah, chapter on the conditions of nikah. The witnesses must hear both sides together and understand the words.
- Mukhtasar Khalil with al-Sharh al-Kabir, Bab al-Nikah, on witnesses. The Maliki rule that witnesses are needed before consummation.
This answer is pending review by the scholars on our team. 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.