122. There are three ways of establishing the najÁsah of any object:
1. One should be certain or satisfied that the thing is najis. If one suspects that something may be najis, it is not necessary to avoid it. Accordingly, there is no problem in dining at restaurants and coffee shops where care-free people, and people who do not observe ÔahÁrah and najÁsah, go to eat, as long as one is not certain or satisfied that the food being served is najis.
2. The person possessing the item says that it is najis, provided he is not accused of being a liar. For example, if the wife, or a servant, or a maid says that a particular utensil or any other object which is in her possession, is najis, it will be accepted as najis, provided she has not been accused of being a liar.
If two just persons testify that a certain thing is najis, rather if one just person, or a trustworthy person who may not be just, says that an item is najis, one must refrain from that item as long as there is no reasonable doubt contrary to his statement.
123. If a person does not know whether a thing is ÔÁhir or najis out of ignorance of its ruling—for example, if he does not know whether blood is ÔÁhir or not—he should inquire about the ruling. Additionally, as long as he has not inquired about it, he should act with precaution. However, if despite knowing the ruling, he doubts whether the item is ÔÁhir or not—for example, he doubts whether a substance is blood or something else, or knows it to be blood, but does not know if it is the blood of a mosquito or a human being—it is ÔÁhir and he does not have to inquire about it.
124. If a thing was initially najis, and then one doubts whether it has become ÔÁhir or not, it will be considered najis. Conversely, if a thing was initially ÔÁhir, and then one doubts whether it has become najis or not, it will be considered ÔÁhir. Additionally, even if it is possible for him to find out whether it is najis or ÔÁhir, it will not be necessary for him to investigate.
125. If a person knows that one of the two vessels or dresses that he possesses is najis, but does not know which one in particular is najis, he must refrain from both of them. However, if he knows that either his own dress is najis or a dress which is not in his possession, he does not have to refrain from his own dress.