Question

There are cases where the Rasul did not spell out specific criteria for a certain condition/situation.For example the minimum distance travelled to qualify as a musafir.In this instant,for example would the criteria to be a traveller depends what the uruf of the society regards the condition of a traveller.Or would it depends on the individual judgment and situation i.e. if he travels in a comfortable car, the distance to qualify as a musafir would be much further than if he travels by foot.