One of the important topics among all Moslems and also Shi’a Moslems is performing the prayer, and the most important thing which a person who prays should observe it, is correct pronunciation of prayer phrases (eloquent Arabic) and considering vocalization rules in recitation of prayer, whereas a letter would not be diverted to another letter.
  Any obligated person (Mokallaf) is faced with two categories and acts in the domain of recitation of prayer and its phrases: one is observing the accuracy of recitation which is obligatory according to the opinions of all great jurisprudents, and if it would not be observed, the prayer becomes void; the other is virtues of vocalization (Tajvid) in recitation of prayer and its phrases, which although the jurisprudents have different views about it, but it is important and its observing in recitation of prayer is admirable and worthy and it is recommended.
  In this writing, while trying to divide vocalization topics, we will determine that in recitation of prayer, which vocalization teachings are obligatory and which ones are recommended.
  In this article we have dealt with examining vocalisation in prayer from the viewpoints of Imamiyyah jurisprudents and our method in this writing is based on documentary and library approach.