The Adhan Definition according to Shi’a View
Shi’a sources state that it is Muhammad who, according to God’s command, ordered the adhan as a means of calling Muslims to prayer. Shi’a Islam teaches that no one else contributed, or had any authority to contribute, towards the composition of the adhan.
Other Shi’a sources state that Bilal ibn Ribah was, in fact, the first person to recite the adhan publicly out loud in front of the Muslim congregation.
Fundamental phrase” La- ilaha-ill-al-lah” is foundation stone of Islam the belief that “there is no god but The God”.This is confession of “Tawhid”.
The phrase” Mohammad-un –rasul-al-lah” fulfil the requirement that there should be some one to guide in the name of The God, which tells”Mohammad is The God’s “rasul” “nabi” the messanger ,Apostle”. This is acceptance of “Nabuvat” of Mohammad.
Nabi Mohammad declared Ali bin Abu Talib as his successor at place called Ghadir Khumm , which was required for the continuation of His guidance,that’s why he told that ”for whoever I am a ’Moula’ of them Ali is his ‘Moula’”(This is also as per article saying of hadith of the pond of Khumm.Hence, the Azaan/kalma required further confession the phrase “Ali-un- vali-ul-lah” means “Ali is his(Allah’s) “Wali “ the “friend” stressing the need that for continuation of faith there is requirement of “Wali” which is one and only “Imam after Imam ” which are realy taking care of Islaam, hence This is also confession of “ Imamat.”
In one of the Qiblah of Imam mustansir (1035-1094)of Fatemi era masjid of Qahira (Mosque of Ahmed-ibn-tulun) engraved his name and “kalema‐tut‐ sahadat”(pl.see right) as ‘La ‐ilah‐ ilal‐lah, Mohamad‐un‐ rasul‐al‐lah Ali –un‐ Wali ‐ ul –lah’.
Azaan remind to everyone, these three Islamic teaching “Tauhid”, “Nabuwat” and “Imamate” before each prayer. These three emphasise Devotion to god, his Nabi Mohammad and Imam, which are so linked together that these can not be viewed separately.One leads to other and finally to the God.
{“I testify that [Aliyun] is the vicegerent of THE GOD” apparently isn’t a part of the Adhan because if it was, there would be no test for the people to see if they will believe in the truth “the guardianship of ALi” or not..if it was a part..the answer of the exam would be before the eyes of the muslims and thereupon everyone will follow the guardianship of Imam Ali without doing the test. Yet, this testification is an essential part of faith..it is an obligatory part of Al-Islam and the belief. that is why it the one who knows it, realizes that it is {indeed} a part of Al-ATHAN and a must in Al-Islam.} (a personal opinion).
The phrase is optional to some shia as justified above. They feel that Ali’s ‘Valayat’ is self-evident ,a testification and need not be declared . However, the greatness of Allah is also taken to be self-evident, but Muslims still declare ‘Allaho Akabar’ to publicize and confirm/boost their faith. This is the reason Fatimid/Dawoodi Bohra gives for recitation of the phrase regarding Ali.
Source: http://en.wikipedia.org/wiki/Adhan
See also: Idul Fitri, Hamper Hari Raya, Hari Raya Hampers