Short answer
The saying comes from a hadith: when a servant marries, he has completed half of his religion, so let him fear Allah in the other half. It is not in Bukhari or Muslim. It is reported by al-Bayhaqi and al-Tabarani, and many scholars accept it as hasan through its chains together. It means marriage guards a person from many sins, not that it replaces worship.
Marriage is sunnah mu'akkadah in normal circumstances and becomes wajib for someone who fears falling into zina and can afford it. Hanafi scholars use the 'half of the deen' hadith as encouragement (targhib), not as a legal proof.
Other madhhabs
- Shafi'i
- For someone with no need of marriage, devoting himself to worship is better; marriage is recommended for one who desires it and can afford it.
Explanation
The hadith says that when a person marries, they have completed half of the religion, and should fear Allah in the remaining half. Its chains are individually weak, but scholars such as al-Albani graded it hasan when they are taken together. So it is a fair basis for encouragement, though not for a ruling.
Its meaning fits authentic hadith. The Prophet ﷺ promised Paradise to whoever guards what is between his jaws and what is between his legs. Scholars explain that the tongue and stomach on one side, and sexual desire on the other, are behind most sins. Marriage takes care of one of the two, which is why it is called half.
He also said: "O young men, whoever of you can afford marriage, let him marry, for it lowers the gaze and guards chastity, and whoever cannot, let him fast." Allah made marriage a source of tranquillity, love and mercy (30:21), and told the community to help the unmarried to marry (24:32).
What it does not mean:
- Single people, widows, divorcees and converts waiting to marry are not "half Muslims". Their faith is judged by their own deeds.
- Marriage does not cancel the duty of prayer, fasting and good character. The hadith itself says to fear Allah in the other half.
- It is not a reason to rush into an unsuitable marriage. See questions to ask.
See is marriage obligatory and hadith about marriage.
The evidence
Quran, Surah Ar-Room 30:21
وَمِنْ ءَايَٰتِهِۦٓ أَنْ خَلَقَ لَكُم مِّنْ أَنفُسِكُمْ أَزْوَٰجًۭا لِّتَسْكُنُوٓا۟ إِلَيْهَا وَجَعَلَ بَيْنَكُم مَّوَدَّةًۭ وَرَحْمَةً ۚ إِنَّ فِى ذَٰلِكَ لَءَايَٰتٍۢ لِّقَوْمٍۢ يَتَفَكَّرُونَ ﴿٢١﴾
And of His signs is that He created for you from yourselves mates that you may find tranquillity in them; and He placed between you affection and mercy. Indeed in that are signs for a people who give thought.
Marriage brings tranquillity and love.
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.
The community should help people marry.
Sahih al-Bukhari 5065
Sahih... يا معشر الشباب من استطاع منكم الباءة فليتزوج ...
"O young men, whoever of you can afford marriage, let him marry."
Marriage protects chastity.
Sahih al-Bukhari 6474
Sahih... من يضمن لي ما بين لحييه وما بين رجليه أضمن له الجنة ...
"Whoever guarantees me what is between his jaws and what is between his legs, I guarantee him Paradise."
Guarding desire is a great part of the deen, which explains 'half'.
Where the ruling is recorded
- al-Durr al-Mukhtar, Kitab al-Nikah, opening section. Marriage is sunnah mu'akkadah normally and wajib or fard with fear of zina.
- Minhaj al-Talibin (Nawawi), Kitab al-Nikah, opening. The Shafi'i view that worship is better for one with no need of marriage.
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.