Short answer
Najis means ritually impure: a substance such as urine, stool, blood or wine that must be washed off the body, clothes and place of prayer. The noun is najasah (impurity), and the opposite is tahir (pure). Not every haram thing is najis: poison or stolen food is haram but pure.
Najasah haqiqiyyah (physical impurity) is any substance the Shariah declares impure. Removing it from the body, clothes and place of prayer, beyond the excused amount, is a condition of salah. Hanafi scholars divide it into heavy (ghalizah) and light (khafifah).
Other madhhabs
- Shafi'i
- Semen is pure; the dog and pig are the heaviest impurity.
- Maliki
- Every living animal, including the dog and pig, is pure, and so is a dog's saliva.
- Hanbali
- Semen is pure, and so are the urine and dung of animals whose meat is eaten.
Explanation
Najis (also written najs or nijs) is an Arabic word meaning impure. In fiqh it describes things that are unclean in themselves, like urine, and things that have become unclean, like a shirt with urine on it. The second kind is called mutanajjis and becomes pure again when washed. Tahir means pure, and tahur means pure and also able to purify, like plain water.
The main impurities in the Hanafi school:
- human urine and stool, and the droppings of animals, except birds like pigeons and sparrows
- flowing blood, pus, and vomit that fills the mouth
- semen, madhy (pre-seminal fluid) and wadi
- wine (khamr) (see alcohol and najis)
- the pig, and the saliva of a dog
- dead animals that were not slaughtered, except fish and creatures without flowing blood
Things that are pure: human sweat, saliva, tears and mucus; the body of every living person, Muslim or not; a cat's body; and clean earth. Najis and haram are different: haram means forbidden. Every najis thing is haram to eat, but many haram things are not najis, such as poison, silk clothing for men, or food bought with stolen money.
Hadath, the state that needs wudu or ghusl, is a different thing from najasah: see hadath and najasah. For how much impurity is excused, see types of najis.
The evidence
Quran, Surah Al-Muddaththir 74:4
وَثِيَابَكَ فَطَهِّرْ ﴿٤﴾
And your clothing purify
Commands keeping clothes clean of impurity.
Sahih al-Bukhari 218
Sahih... أما أحدهما فكان لا يستتر من البول ...
"As for one of them, he did not protect himself from urine."
Carelessness with impurity is a cause of punishment in the grave.
Where the ruling is recorded
- al-Hidaya, Kitab al-Taharat, chapter on impurities and their purification. Defines heavy and light impurity and how each is removed.
- Nur al-Idah with Maraqi al-Falah, Kitab al-Taharah, chapter on impurities and their removal. Lists the impure substances.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. 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.