Short answer
Three days for a relative, and four months and ten days for a widow (or until she gives birth if she is pregnant). Grief itself has no limit, but outward mourning, such as leaving adornment and normal life, should not go past three days except for a wife whose husband died.
A woman may observe mourning (hidad) for a relative for up to three days. A widow must observe hidad for the full iddah of four months and ten days, or until birth if pregnant. Condolence visits are for three days, and repeating condolence after that is makruh except for someone who was away.
The four schools agree on this.
Explanation
Islam allows grief and honours it. What it limits is the outward mourning, called hidad: leaving adornment, perfume and fine clothes, and stopping normal life. The four schools agree on the limits below.
- Three days for the death of a parent, child, sibling or other relative.
- Four months and ten days for a widow whose husband has died.
- Until she gives birth, if the widow is pregnant.
After three days, the family should go back to their normal routine, even if the heart is still heavy. This is not a rule against sadness. You may still cry, miss them and make dua for years. It is a rule against holding yourself in public mourning, wearing only black, refusing to eat or celebrate Eid, and the customs that keep the wound open.
For condolence, people visit the family within three days. After that, condolence is not repeated, except for someone who was travelling or did not know. See condolence in Islam.
For a widow, the rules of iddah apply for the whole period, including staying in the home at night and avoiding adornment. See what is iddah and what a widow can do during iddah. The iddah calculator gives the end date.
Men do not have a set hidad, but they too should not abandon their duties for long. Grief that becomes depression is an illness and deserves care; see depression in Islam.
The evidence
Quran, Surah Al-Baqara 2:234
وَٱلَّذِينَ يُتَوَفَّوْنَ مِنكُمْ وَيَذَرُونَ أَزْوَٰجًۭا يَتَرَبَّصْنَ بِأَنفُسِهِنَّ أَرْبَعَةَ أَشْهُرٍۢ وَعَشْرًۭا ۖ فَإِذَا بَلَغْنَ أَجَلَهُنَّ فَلَا جُنَاحَ عَلَيْكُمْ فِيمَا فَعَلْنَ فِىٓ أَنفُسِهِنَّ بِٱلْمَعْرُوفِ ۗ وَٱللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌۭ ﴿٢٣٤﴾
And those who are taken in death among you and leave wives behind - they, [the wives, shall] wait four months and ten [days]. And when they have fulfilled their term, then there is no blame upon you for what they do with themselves in an acceptable manner. And Allah is [fully] Acquainted with what you do.
This sets the widow's waiting and mourning period.
Sahih al-Bukhari 1280
Sahih... لا يحل لامرأة تؤمن بالله واليوم الآخر أن تحد على ميت فوق ثلاث ...
"It is not lawful for a woman who believes in Allah and the Last Day to mourn a dead person for more than three days, except for a husband."
This sets the three day limit and the widow's exception.
Sahih al-Bukhari 1303
Sahih... إن العين تدمع والقلب يحزن ولا نقول إلا ما يرضى ربنا ...
"The eye weeps and the heart grieves, but we say only what pleases our Lord."
Grief is allowed; only displeasing words are not.
Where the ruling is recorded
- al-Hidaya, Kitab al-Talaq, Bab al-Iddah, Fasl fi al-Hidad. The widow's mourning and its rules.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, Bab Salat al-Janazah. Condolence for three days and the dislike of repeating it after.
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.