The Azaan was started as a practice after the migration of the Holy Prophet (SAW) and his followers to Medina. How Adhan Started According To Islam is an important part of islam. The early Muslims required an efficient means of call to the prayer for the congregation and various strategies were proposed.
The Vision of Abdullah ibn Zayd
The dream that Abdullah ibn Zayd (RA), companion of the Prophet had one night was that he saw a man puttimg on green cloths and the man had a bell with him. Abdullah ibn Zayd in the vision asked the man if he could ring the bell for offering prayers. The man in the vision wanted to teach Abdullah the correct way of calling for prayer instead of a whistle, he described to him the words in Azaan.
Another concerns Abdullah ibn Zayd narrating a vision to the Prophet Muhammad (SAW) and the prophet confirming it as an actual vision. The Prophet then, asked Bilal ibn Rabah (RA) a freed slave who had the most enchanting voice to recite the Azaan using the translated words from the vision.

Hadith About The Adhan
Several Hadiths describe the events leading to the establishment of the Azaan:
Hadith from Sunan Abi Dawood
One of the narrations found in Sunan Abi Dawood states:
Narrated Abdullah ibn Zayd ibn Abd Rabbih:
“When the Prophet (SAW) ordered a bell to be made so that it could be struck to gather the people for prayer, a man carrying a bell in his hand appeared to me while I was asleep. I said: O servant of Allah, will you sell the bell? He said: What will you do with it? I said: We will call the people to prayer. He said: Should I not guide you to something better than that? I said: Yes. He said: You should say: Allahu Akbar, Allahu Akbar, Allahu Akbar, Allahu Akbar, Ashhadu an la ilaha illallah, Ashhadu an la ilaha illallah, Ashhadu anna Muhammadar Rasulullah, Ashhadu anna Muhammadar Rasulullah, Hayya ‘ala-s-Salah, Hayya ‘ala-s-Salah, Hayya ‘ala-l-Falah, Hayya ‘ala-l-Falah, Allahu Akbar, Allahu Akbar, La ilaha illallah.”
When the morning came, I went to the Messenger of Allah (SAW) and informed him of what I had seen. He said: It is a true vision, Insha’Allah. He then commanded Bilal (RA) to pronounce the Azaan, saying that he had a louder voice than I did. So I got up with Bilal (RA) and began to teach him the words, and he pronounced them. Umar ibn al-Khattab (RA) heard the Azaan while he was in his house, and he came out with his cloak on, saying: By Him Who has sent you with the truth, I also saw the same (dream) as has been revealed.”
Another Hadith from Sahih al-Bukhari mentions
Narrated Ibn Umar (RA):
“When the Muslims arrived in Medina, they used to assemble for the prayer, and used to guess about the time for it. During those days, the practice of Azaan for the prayers had not been introduced yet. Once they discussed this problem regarding the call for prayer. Some people suggested the use of a bell like the Christians, others proposed a trumpet like the horn used by the Jews, but Umar (RA) was the first to suggest that a man should call (the people) for the prayer; so Allah’s Messenger (SAW) ordered Bilal (RA) to get up and pronounce the Azaan for prayers.”
Significance of the Adhan
The Azaan has a very important role in islam not only prays the Muslims but also declaring the main doctrines of the religion. The words in the Azaan are The testimony of the Oneness of Allah, and the prophethood of Muhamad, whatsoever happened around Muslims is a reminder of their religious obligations, and the role of prayers in their lives.

