Short answer
Up to one third of your estate, after funeral costs and debts, and only to people or causes that do not already inherit from you. A bequest to an heir, or of more than a third, is valid only if the other adult heirs agree after your death. Writing a will is sunnah, and it is required if you owe debts or hold trusts.
A wasiyyah (bequest) is valid up to one third of the estate after debts. A bequest to an heir, or above one third, depends on the consent of the adult heirs after the death. A will is mustahabb, and wajib when one has unpaid debts, trusts or obligations such as missed zakat or fidya.
The four schools agree on this.
Explanation
Islam fixes the shares of the main heirs in the Quran, so a Muslim does not need a will to divide the estate among them. The wasiyyah (bequest) is for the people and causes the fixed shares do not cover. The four schools agree on its main limits.
The rules:
- One third at most. When Sa'd wanted to give away most of his wealth, the Prophet ﷺ said: "A third, and a third is a lot." Leaving your heirs well off is better than leaving them in need.
- Not to an heir. "No bequest for an heir": a spouse, child or parent already has their share. If you leave them extra, it only stands if the other adult heirs agree after your death.
- After debts. The third is counted from what is left after funeral costs and debts.
Who you can leave the third to:
- Relatives who do not inherit, such as grandchildren whose parent died before you, nieces and nephews, or in-laws.
- An adopted child or a stepchild.
- A non-Muslim parent, spouse or relative, who cannot inherit by law.
- Charity, a mosque, a school, or sadaqah jariyah.
Living in the West. If you die without a legal will, the law in the US, UK and Canada divides your estate by its own rules, which can give your spouse or others a share different from the Quran. A legally valid Islamic will avoids this. Use the Islamic will builder to prepare one and have it witnessed as your local law requires.
A will can also record your wish for a Muslim burial, your debts, and your guardianship wishes for children. Every family is different, so ask a mufti and a local lawyer to check yours.
Ask a mufti about your own case. This answer explains the general ruling. When the details of your situation matter, as they do here, ask a qualified mufti and give them the full facts. Where to ask a scholar.
The evidence
Quran, Surah Al-Baqara 2:180
كُتِبَ عَلَيْكُمْ إِذَا حَضَرَ أَحَدَكُمُ ٱلْمَوْتُ إِن تَرَكَ خَيْرًا ٱلْوَصِيَّةُ لِلْوَٰلِدَيْنِ وَٱلْأَقْرَبِينَ بِٱلْمَعْرُوفِ ۖ حَقًّا عَلَى ٱلْمُتَّقِينَ ﴿١٨٠﴾
Prescribed for you when death approaches [any] one of you if he leaves wealth [is that he should make] a bequest for the parents and near relatives according to what is acceptable - a duty upon the righteous.
The early command to bequeath, later shaped by the inheritance verses.
Quran, Surah An-Nisaa 4:12
۞ وَلَكُمْ نِصْفُ مَا تَرَكَ أَزْوَٰجُكُمْ إِن لَّمْ يَكُن لَّهُنَّ وَلَدٌۭ ۚ فَإِن كَانَ لَهُنَّ وَلَدٌۭ فَلَكُمُ ٱلرُّبُعُ مِمَّا تَرَكْنَ ۚ مِنۢ بَعْدِ وَصِيَّةٍۢ يُوصِينَ بِهَآ أَوْ دَيْنٍۢ ۚ وَلَهُنَّ ٱلرُّبُعُ مِمَّا تَرَكْتُمْ إِن لَّمْ يَكُن لَّكُمْ وَلَدٌۭ ۚ فَإِن كَانَ لَكُمْ وَلَدٌۭ فَلَهُنَّ ٱلثُّمُنُ مِمَّا تَرَكْتُم ۚ مِّنۢ بَعْدِ وَصِيَّةٍۢ تُوصُونَ بِهَآ أَوْ دَيْنٍۢ ۗ وَإِن كَانَ رَجُلٌۭ يُورَثُ كَلَٰلَةً أَوِ ٱمْرَأَةٌۭ وَلَهُۥٓ أَخٌ أَوْ أُخْتٌۭ فَلِكُلِّ وَٰحِدٍۢ مِّنْهُمَا ٱلسُّدُسُ ۚ فَإِن كَانُوٓا۟ أَكْثَرَ مِن ذَٰلِكَ فَهُمْ شُرَكَآءُ فِى ٱلثُّلُثِ ۚ مِنۢ بَعْدِ وَصِيَّةٍۢ يُوصَىٰ بِهَآ أَوْ دَيْنٍ غَيْرَ مُضَآرٍّۢ ۚ وَصِيَّةًۭ مِّنَ ٱللَّهِ ۗ وَٱللَّهُ عَلِيمٌ حَلِيمٌۭ ﴿١٢﴾
And for you is half of what your wives leave if they have no child. But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt. And for the wives is one fourth if you leave no child. But if you leave a child, then for them is an eighth of what you leave, after any bequest you [may have] made or debt. And if a man or woman leaves neither ascendants nor descendants but has a brother or a sister, then for each one of them is a sixth. But if they are more than two, they share a third, after any bequest which was made or debt, as long as there is no detriment [caused]. [This is] an ordinance from Allah, and Allah is Knowing and Forbearing.
A bequest must not be used to harm the heirs.
Sahih al-Bukhari 2742
Sahih... الثلث والثلث كثير ...
"A third, and a third is a lot."
The bequest is limited to one third.
Sunan Abi Dawud 2870
Graded hasan sahih... إن الله قد أعطى كل ذي حق حقه فلا وصية لوارث ...
"Allah has given everyone with a right their right, so there is no bequest for an heir."
Heirs do not receive a bequest on top of their share.
Sahih al-Bukhari 2738
Sahih... ما حق امرئ مسلم له شيء يوصي فيه يبيت ليلتين إلا ووصيته مكتوبة عنده ...
"A Muslim who has something to bequeath should not spend two nights without his will written down."
Writing a will is encouraged.
Where the ruling is recorded
- al-Hidaya, Kitab al-Wasaya. The one third limit and bequests to heirs depending on the heirs' consent after death.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Wasaya. When a will is wajib and bequests to non-Muslims.
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.