The Sunni View of Adhan

Sunnis state that the adhan was not written or said by the Islamic prophet, Muhammad, but by one of his Sahabah (his companions). Umar, a prominent sahabah of Muhammad, had a vision in his dream, in which the call for prayers was revealed to him by God. He later related this to his companions. Meanwhile, this news reached Muhammad, and he liked it and confirmed it. Because of his stunning voice Muhammad choose a freed Habeshan slave by the name of Bilal ibn Ribah to give the call for prayers. Muhammad preferred the call better than the use of bells (as by the Christians) and horns (as by the Jews).

During the Friday prayer (Salat Al Jumu’ah), there are two adhans; the first is to call the people to the mosque, the second is said before the Imam begins the khutbah (sermon). Just before the prayers start, someone amongst the praying people recites the iqama as in all prayers. The basis for this is that at the time of the Caliph Umar he ordered 2 adhans to be made, the first of which was to be made in the marketplace to inform the people that the Friday prayer was soon to begin, and the second adhan would be the regular one held in the mosque. Not all Sunnis prefer two adhans as the need for warning the people of the impending time for prayer is no longer essential now that the times for prayers are well known.

Source: http://en.wikipedia.org/wiki/Adhan

See also: Lebaran, Hari Raya, Ramadan Gift