Janabah (Arabic: جنابة) refers to a state of spiritual impurity that occurs due to sexual intercourse or the discharge of semen. It necessitates a ritual ablution (ghusl) of the entire body. A person on whom Ghusl of Janabat has become obligatory is called a junub.
References in the Qur'an
يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا قُمْتُمْ إِلَى الصَّلَاةِ فَاغْسِلُوا وُجُوهَكُمْ وَأَيْدِيَكُمْ إِلَى الْمَرَافِقِ وَامْسَحُوا بِرُءُوسِكُمْ وَأَرْجُلَكُمْ إِلَى الْكَعْبَيْنِ ۚ وَإِنْ كُنْتُمْ جُنُبًا فَاطَّهَّرُوا
[5:6] O ye who believe! when ye prepare for prayer, wash your faces, and your hands (and arms) to the elbows; Rub your heads (with water); and (wash) your feet to the ankles. If ye are in a state of ceremonial impurity, bathe your whole body. . .
يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَقْرَبُوا الصَّلَاةَ وَأَنْتُمْ سُكَارَىٰ حَتَّىٰ تَعْلَمُوا مَا تَقُولُونَ وَلَا جُنُبًا إِلَّا عَابِرِي سَبِيلٍ حَتَّىٰ تَغْتَسِلُوا
[4:43] O ye who believe! Approach not prayers with a mind befogged, until ye can understand all that ye say,- nor in a state of ceremonial impurity (Except when travelling on the road), until after washing your whole body. . .
Causes of Janabah
There are two events that lead to entering the state of janabah. The first is through ejaculation, no matter how this happens. It does not make a difference whether the individual is awake or asleep, if it happened through lawful means or unlawful means (masturbation), or if it was intentional or unintentional. In every scenario that semen is discharged, a man will enter the state of janabah and the ghusl of janabat will become obligatory on him. If a woman ejaculates, then as an obligatory precaution she should also do the ghusl of janabat provided that the discharge came with sexual passion and she felt relaxed after it (i.e. orgasm/climax). But if the secretion lacks sexual passion and she does not attain a feeling of relaxation after the discharge, then the discharge is not considered impure and an ablution is not obligatory upon her. When a woman reaches orgasm and a fluid is discharged from her, she becomes junub and ghusl of janābah becomes obligatory for her. However, if she doubts whether she has reached this stage, or whether there was a discharge, ghusl does not become obligatory on her. 
A narration pertaining to the ghusl of janabah for women is as follow:
وعن محمد بن يحيى ، عن أحمد بن محمد ، عن محمد بن إسماعيل بن بزيع قال : سألت الرضا ( عليه السلام ) عن الرجل يجامع المرأة فيما دون الفرج وتنزل المرأة هل عليها غسل ؟ قال : نعم
And from Muhammad bin Yahya, from Ahmad bin Muhammad, from Muhammad bin Ismaeel Bazi', who said: "I asked Imam al-Ridha about the man if he has sex with a woman without the vagina, and the woman ejaculates, does she have to do ghusl?" He said: "Yes. "
The second event that causes one to enter the state of janabah is through sexual intercourse. It does not make a difference whether the intercourse was lawful or not, or whether ejaculation accompanied the act. In the case of sexual intercourse, ghusl becomes obligatory on both the man and the woman.
Forbidden and Disliked Acts for a Junub
The following five things are forbidden (haraam) for a junub:
- To touch with any part of one's body the script of the Holy Qur'an and/or the Name of Almighty Allah in whichever language it may be. And it is better that the names of the holy Prophet and Imams and Lady Fatima Zahra (peace be upon them) should also not be touched in that condition.
- Entering Masjid ul-Haraam in Makkah or Masjid al-Nabawi in Medina, even though it may be only passing from one gate and going out of another.
- To stay or halt in all other mosques, and similarly, on the basis of obligatory precaution, to stay in the shrines of the holy Imams. However, there is no harm if one crosses or traverses through a mosque, entering from one gate and exiting from another.
- To enter a mosque with an intention of lifting away something or placing something in it.
- To recite those verses of the holy Qur'an on the recitation of which performance of prostration becomes obligatory. These verses occur in four surahs of the holy Qur'an: 32:15; 41:38; 53:62 and 96:19
The following nine things are disliked (makruh) for a junub:
- To eat
- To drink. But if the junub washes his or her face, hands and mouth, then eating or drinking in that state will not be Makruh. And if he or she washes the hands only, then unworthiness of the acts is reduced.
- To recite more than seven verses of the holy Qur'an other than those in which obligatory prostration occur
- To touch the cover, the margin or border of the holy Qur'an or the space between its lines, with any part of one's body
- To keep the Holy Qur'an with oneself
- To sleep
- To dye one's hair with henna
- To apply oil on one's body
- To have sexual intercourse after a nocturnal emission
- ↑ The Major Ablution (Ghusl Janabat) Islamic Marriage, by Syed Akthar Husain S.H. Rizvi
- ↑ Rules of the Ghusl of Janābah Practical Laws of Islam, Sayyid Ali Khamenei
- ↑ Wasa'il Al-Shi'a. Volume 2 Chapters of Janabah
- ↑ Forbidden acts for those in Janabat Islamic Laws, Ayatullah Ali al-Sistani
- ↑ Things which are Makrooh for Junub Ibid