Short answer
For most people marriage is a strong sunnah, not fard. It becomes wajib for someone with strong desire who can afford it and fears zina, and it is disliked or even haram for someone sure he would wrong a spouse. Not marrying is not a sin in itself. The schools differ on whether marriage or extra worship is better for someone with no need.
In a normal state nikah is sunnah mu'akkadah. It is wajib for one with strong desire, the means and a fear of zina, fard if he is certain he will fall into zina without it, makruh tahrimi if he fears he will wrong his wife, and haram if he is certain of it. For the Hanafis, marrying is better than staying single for voluntary worship.
Other madhhabs
- Shafi'i
- Marriage is recommended for someone who needs it and can afford it. For someone without need, devoting himself to worship is better.
- Hanbali
- Marriage is better than voluntary worship for anyone with desire. One narration from Imam Ahmad makes it wajib for anyone with desire who can afford it.
Explanation
The Quran commands, "marry the unmarried among you" (24:32), and the Prophet ﷺ made marriage part of his sunnah. When some Companions wanted to stay single to pray all night and fast every day, he told them that he prays and sleeps, fasts and breaks his fast, and marries women, and that whoever turns away from his sunnah is not from him. Islam has no monks.
- Strong sunnah for most people.
- Wajib if your desire is strong, you can pay the mahr and support a spouse, and you fear zina.
- Fard if you are sure you will fall into zina without it.
- Disliked if you fear you will wrong a spouse, for example by not providing or by harshness.
- Haram if you are sure you would wrong them.
Is it a sin not to marry? Not in itself. A person who has no means, has health reasons, or simply has not found the right spouse is not sinning. The Prophet ﷺ told young people who cannot yet marry to fast, because fasting curbs desire. What is sinful is falling into zina or the steps that lead to it.
Families and delays. Families sometimes delay a ready young person's marriage for degrees, money or a big wedding. Where this pushes the young person towards haram, scholars warn the family against it. A simple nikah is enough. See marrying young and the purpose of marriage.
The evidence
Quran, Surah An-Noor 24:32
وَأَنكِحُوا۟ ٱلْأَيَٰمَىٰ مِنكُمْ وَٱلصَّٰلِحِينَ مِنْ عِبَادِكُمْ وَإِمَآئِكُمْ ۚ إِن يَكُونُوا۟ فُقَرَآءَ يُغْنِهِمُ ٱللَّهُ مِن فَضْلِهِۦ ۗ وَٱللَّهُ وَٰسِعٌ عَلِيمٌۭ ﴿٣٢﴾
And marry the unmarried among you and the righteous among your male slaves and female slaves. If they should be poor, Allah will enrich them from His bounty, and Allah is all-Encompassing and Knowing.
A general command to help people marry.
Quran, Surah An-Noor 24:33
وَلْيَسْتَعْفِفِ ٱلَّذِينَ لَا يَجِدُونَ نِكَاحًا حَتَّىٰ يُغْنِيَهُمُ ٱللَّهُ مِن فَضْلِهِۦ ۗ وَٱلَّذِينَ يَبْتَغُونَ ٱلْكِتَٰبَ مِمَّا مَلَكَتْ أَيْمَٰنُكُمْ فَكَاتِبُوهُمْ إِنْ عَلِمْتُمْ فِيهِمْ خَيْرًۭا ۖ وَءَاتُوهُم مِّن مَّالِ ٱللَّهِ ٱلَّذِىٓ ءَاتَىٰكُمْ ۚ وَلَا تُكْرِهُوا۟ فَتَيَٰتِكُمْ عَلَى ٱلْبِغَآءِ إِنْ أَرَدْنَ تَحَصُّنًۭا لِّتَبْتَغُوا۟ عَرَضَ ٱلْحَيَوٰةِ ٱلدُّنْيَا ۚ وَمَن يُكْرِههُّنَّ فَإِنَّ ٱللَّهَ مِنۢ بَعْدِ إِكْرَٰهِهِنَّ غَفُورٌۭ رَّحِيمٌۭ ﴿٣٣﴾
But let them who find not [the means for] marriage abstain [from sexual relations] until Allah enriches them from His bounty. And those who seek a contract [for eventual emancipation] from among whom your right hands possess - then make a contract with them if you know there is within them goodness and give them from the wealth of Allah which He has given you. And do not compel your slave girls to prostitution, if they desire chastity, to seek [thereby] the temporary interests of worldly life. And if someone should compel them, then indeed, Allah is [to them], after their compulsion, Forgiving and Merciful.
Those who cannot yet marry are told to stay chaste, so being unmarried is not itself a sin.
Sahih al-Bukhari 5063
Sahih... فمن رغب عن سنتي فليس مني ...
"Whoever turns away from my sunnah is not from me."
Turning away from marriage as a way of piety is rejected.
Sahih al-Bukhari 5066
Sahih... ومن لم يستطع فعليه بالصوم فإنه له وجاء ...
"Whoever is not able, let him fast, for it is a shield for him."
The guidance for those who cannot yet marry.
Where the ruling is recorded
- al-Durr al-Mukhtar with Radd al-Muhtar, Kitab al-Nikah, opening discussion. The ruling of nikah moves between fard, wajib, sunnah, makruh and haram according to a person's state.
- al-Hidaya, Kitab al-Nikah, opening chapter. Nikah is a sunnah mu'akkadah and better than devoting oneself to voluntary worship.
- Minhaj al-Talibin (Nawawi), Kitab al-Nikah. The Shafi'i view that marriage is recommended for one who needs it and can afford it.
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.