How a pure thing becomes impure:
1. * If a Pak (pure item/clothes) thing touches a najis thing and if either or both of them are so wet that the wetness of one reaches the other, the Pak thing will become najis. Similarly, if the wetness of the thing which has become najis, touches a third thing, that t hird thing will also become najis. It is commonly held by the scholars, that a thing which has become najis transmits its najasat, but indefinite number of transmissions is improbable. In fact, after certain stage it is Pak. For example, if the right hand of a person becomes najis with urine, and then, while still wet, it touches his left hand, the left hand will also become najis. Now, if the left hand after having dried up, touches a wet cloth, that cloth will also become najis, but, if that cloth touc hes another wet thing, it cannot be said to be najis. In any case, if the wetness is so little, that it does not affect the other thing, then the Pak thing will not become najis, even if it had contacted the Najisul Ayn.
2. If a Pak thing touches a najis thing and one doubts whether either or both of them were wet or not, the Pak thing does not become najis.
3. * If there are two things and one does not know which of them is Pak, and which is najis, and later a damp Pak thing touches one of them, that thing does not become najis.
4. If the ground, cloth, or similar things are wet, then only that part will become najis where najasat reaches, and the remaining part will remain Pak. Same is the case with melon, cucumber etc.
5. When a syrup or ghee is in a fluid state, in a manner that if some quantity of it is removed, it does not leave an empty trace, the entire quantity will become najis immediately when even their slightest part becomes najis. But if it has solidified, and when some part of it is removed, a trace of emptiness is seen, then only that part will be najis which has come in contact with najasat, even if the empty trace gets filled up later. So, if the droppings of a rat fall on it, only that part will becom e najis on which the droppings have fallen, and the rest will remain Pak.
6. If a fly or an insect sits on wet, najis thing, and later sits on wet, Pak thing, the Pak thing will become najis, if one is sure that the insect was carrying najasat with it, and if one is not sure, then it remains Pak.
7. If a part of one’s body which is perspiring becomes najis, all those parts to which the sweat reaches, will become najis. Where it does not reach will remain Pak.
8. * If there is blood in the phlegm, or substance which comes out of the nose or throat, the part with blood will be najis, and the remaining part will be Pak. Hence, if these substances come out of the mouth, or the nose, the part about which one is sure that najasat has reached, will be najis, and the part about which one is doubtful whether najasat has reached it or not, will be considered Pak.
9. * If an ewer or a vessel with a hole in its bottom, is placed on najis ground, and its water ceases to flow, allowing water to collect under it, till it is seen as one with the water inside the vessel, the water in the vessel will be najis. However , if the water inside the vessel continues to flow forcefully, it will not become najis.
10. If a thing enters the body reaching najasat, but has no trace of it when brought out of the body, it is Pak. Hence, if the apparatus of enema, or its water, enters one’s rectum, or a needle or knife, or any other similar thing, is driven into the bo dy and has no trace of najasat when it is taken out later, it is not najis. Same is the case with sputum and mucus of the nose, if it contacts blood within the body, but does not have any trace of blood when it comes out of the body.