There is a difference of opinion among Muslims scholars as to what type of things are considered impure (najas). The evidences behind their conclusions are discussed in more advanced classes. In the Hanbali school, the following things are considered impure (najas):
- Any intoxicating liquid
- This includes any hashisha that intoxicates
- Any bird or animal that is not allowed to be eaten and is larger than a cat
- Examples: lions, wolves, dogs, pigs, eagles, elephants, vultures, etc.
- Anything originating from such animals is also considered impure, such as, their saliva, snot, meat, milk, sperm, urine, feces, etc.
- Any carcass that has flowing blood is impure after its death even if it is smaller than a cat
- Examples: mice, snakes, frogs, geckos, etc. are impure after their death even though they are pure while alive
- The following are exceptions, thus, considered pure before and after death: human beings, fish, locusts and any animal or bird that is permissible to eat. For the last category (animals or birds permissible to eat), it is considered pure after death only if it was slaughtered according to Islamic guidelines, otherwise, it will be considered impure
- This also means anything that does not have flowing blood is considered pure whether its alive or dead, such as, spiders, roaches, bugs, flies, mosquito, bees, worms, ants, lice, fleas, etc. If such things contain small amount of blood, then that is tolerated but it must not be flowing blood.
- However, if such insects originate from something impure, then they become impure as well whether they’re alive or dead. For example, if an insect left its eggs in feces and then these eggs hatched.
- The following from a human being are considered impure: blood, pus, urine, feces, pre-ejaculatory fluid (madhi) and vomit
What does it mean in Hanbali law when we say such things are impure? It simply means that we cannot eat them and if their saliva, snot, feces, urine, etc. get on our body, clothes, or floor, then we must wash it out with water. For example, if a dog licks our hand, then we must wash the hand out with water to remove the impurity, otherwise, we cannot pray with that unwashed hand even if the hand dried after a while. It does not mean that we treat the above animals with disrespect or abuse.
There are more details involved to the above general list, but they are discussed in more advanced level books.