Studying the Precedence of Obligation with Substitute in Preferences concerning Disturbance (tazāḥum) and its Legal Referents

Among the preferences brought up on tazāḥum (disturbance, conflict) is that the obligation that does not have a substitute becomes precedent over the obligation possessing substitute. Concerning the proof of this universal major, there are evidences and aspects brought up in methodology of Islamic jurisprudence and two referents have been brought up for this universal major and rule as verification to this principle. In this research, by exploring into four reasons for the aspects stated for proving the major and then study of the two referents that are brought up, it is concluded that if the obligation possesses latitudinal substitute, there would occur no tazāḥum and it stands out of question; and if the obligation possesses a longitudinal substitute, two positions are to be discussed:A. It should be said concerning the proof of major on preferences in the section of disturbance: this case is not acceptable as an independent criterion in preferences with disturbance; rather, the issue should be studied independently in every case and all the evidences and aspects that are stated for approximation of this universal criterion are discredited.
B. Concerning the vacillation between impure (khubthiya) purification and ritual impurity (ḥadathiya) purification, it should be stated that: one cannot clearly use evidences that legal authority is acquired in water purification and thus one cannot make a judgment concerning this criterion for the precedence of khubthiya purification over ḥadathiya purification; rather, one should appeal to another evidence: concerning the vacillation between full performance of on-time prayer with tayammum (ablution with earth or sands) and performance of one rak‘a of on-time prayer with wuḍū (ablution with water), performing tayammum would be precedent to wuḍū only because full performance of on-time prayer is more important