The two adhans for Friday prayer
How many adhans are there for Friday prayer? Is it one, called when the imam
ascends the pulpit, or two—the first made at the time of the call for prayer and the second after the imam ascends the pulpit?
The adhan [call to prayer] is a notification that the time for prayer has begun. Initially, the adhan for Friday prayer was called when the imam had ascended the pulpit. Al-Sa`ib Ibn Yazid (may Allah be pleased with him) said, "During the time of the Prophet , Abu Bakr and 'Umar, the first adhan for Friday prayer was called when the imam had taken his seat on the pulpit. During the caliphate of 'Uthman, when the people increased in number, a third call was added which was made at al-Zawra`. The Prophet had only one muezzin" [recorded by Al-Bukhari, an-Nisa`i and Abu Dawud].
The hadith attests to the legitimacy of the first adhan which is called when the time of Friday prayer (the time of noon) enters as well as for the legitimacy of the second adhan which is called when the imam takes his seat on the pulpit. A group from among the Companions (may Allah be pleased with them) were present when 'Uthman commanded that a third adhan be called at al-Zawra` and they did not contest this action. It was therefore considered a tacit consensus on its admissibility; a tacit consensus is considered definitive evidence as maintained by legal theorists (may Allah be pleased with them all).
Based on the above, the first adhan is permissible based on authentic evidences. The call to Friday prayer is made three times: the first is called when the time of prayer enters and before the imam ascends the pulpit, the second after the imam ascends the pulpit and before he starts the sermon while the third (the iqama) is called for commencing the prayer.
Allah Almighty knows best