Ways of proving Najasat
122. There are three ways of proving the Najasat of anything:
One should be certain, or satisfied that something is Najis. If one suspects that something may be Najis, it is not necessary to avoid it. Accordingly, eating or drinking at cafeterias and guest houses where reckless people and those who don’t pay much attention towards Taharat and Najasat go to eat, if one is not certain or satisfied that the food which has been served to them is Najis, it is permissible to eat.
If a reliable person who possesses, controls or manages a thing, says that it is Najis. For example, if the wife, or a servant, or a maid says that a particular utensil or any other object which she handles is Najis, it will be considered as Najis.
If two just persons testify that a certain thing is Najis, as per obligatory precaution even if one just person testifies about the Najasat of an object one must avoid himself from using it.
123. If a person does not know whether a thing is Pak or Najis because of ignorance, for example, if one does not know whether the sweat of a person who became Mujnib by a Haraam act is Pak or not, he should enquire from those who know. But, if he knows the rule, and doubts the nature of particular thing, like when he doubts whether a thing is blood or not, or if he does not know whether it is the blood of a
mosquito or a human being, the thing is Pak, and it is not necessary to make investigation or enquiry about it.
124. A thing which was originally Najis, and one doubts whether it has become Pak, will be considered as Najis. Conversely, if a thing was originally Pak, and if one doubts whether it has become Najis, it will be considered Pak. And it is not necessary to ascertain, even if it is possible to do so.
125. If a person knows that out of the two vessels used by him, one has become Najis, but cannot identify it, he should refrain from using both of them. But if he does not know which one of the two dresses has become Najis in such case one should pray twice with both the dresses in order to be certain. Indeed, one can't become certain by praying in just one dress. Similarly, if someone prays once by wearing both the clothes the Namaaz will be void.