Short answer
At puberty (bulugh). In the Hanafi school a boy is baligh when he has a wet dream or ejaculates, and a girl when she has her first period, a wet dream or becomes pregnant. With no sign, both are baligh at 15 lunar years, about 14 years and 7 months.
Bulugh is known by its physical signs; the earliest possible age is 12 for a boy and 9 for a girl. If no sign appears, the fatwa is that both become baligh at 15 lunar years, the view of Abu Yusuf and Muhammad. Growth of pubic hair is not a sign in the Hanafi school.
Other madhhabs
- Shafi'i
- 15 lunar years with no sign; growth of coarse pubic hair is a sign only for the children of non-Muslims.
- Hanbali
- 15 lunar years with no sign; growth of coarse pubic hair is a sign.
- Maliki
- 18 lunar years in the well-known view with no sign; coarse pubic hair is a sign.
Explanation
The Prophet ﷺ said the pen is lifted from the child until he grows up. Before bulugh (puberty), a child's sins are not recorded, while good deeds are rewarded. From bulugh the person is mukallaf (legally responsible), as long as they are sane.
The age of 15 comes from Ibn Umar, who was turned away from the battle of Uhud at fourteen and accepted at the Trench at fifteen. Fifteen lunar years is about fourteen years and seven months in the solar calendar. Work out a child's Hijri age with the Hijri age calculator.
What changes at bulugh:
- The five prayers and Ramadan fasts become fard. Missed ones must be made up.
- Ghusl is required after a wet dream or a period.
- Hijab and the rules of awrah apply fully.
- Zakat on the person's own wealth becomes due, in the Hanafi school.
- The person is answerable for their own sins.
Many girls reach puberty at nine to twelve, often before parents expect. Explain periods, ghusl and prayer before the first one comes, so the child knows what to do. See children and fasting and children and prayer.
The evidence
Quran, Surah An-Noor 24:59
وَإِذَا بَلَغَ ٱلْأَطْفَٰلُ مِنكُمُ ٱلْحُلُمَ فَلْيَسْتَـْٔذِنُوا۟ كَمَا ٱسْتَـْٔذَنَ ٱلَّذِينَ مِن قَبْلِهِمْ ۚ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ لَكُمْ ءَايَٰتِهِۦ ۗ وَٱللَّهُ عَلِيمٌ حَكِيمٌۭ ﴿٥٩﴾
And when the children among you reach puberty, let them ask permission [at all times] as those before them have done. Thus does Allah make clear to you His verses; and Allah is Knowing and Wise.
Puberty is the point where adult rules begin.
Jami' at-Tirmidhi 1423
Graded sahih... رفع القلم عن ثلاثة عن النائم حتى يستيقظ ...
"The pen is lifted from three: the sleeper until he wakes, the child until he grows up, and the insane until he is sane."
Children are not held accountable before puberty.
Sahih al-Bukhari 2664
Sahih... ثم عرضني يوم الخندق وأنا ابن خمس عشرة فأجازني ...
"He presented me on the day of the Trench when I was fifteen, and he accepted me."
The basis for fifteen as the age of adulthood when no sign appears.
Where the ruling is recorded
- al-Hidaya, Kitab al-Hajr, chapter on the age of maturity. Signs of bulugh and the age of fifteen.
- al-Durr al-Mukhtar, Kitab al-Hajr, section on bulugh. Minimum ages and the fatwa on fifteen years.
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.