Ibn Umar reported:When the Muslims came to Medina, they gathered and sought to know the time of prayer but no one summoned them. One day they discussed the matter, and some of them said: Use something like the bell of the Christians and some of them said: Use horn like that of the Jews. Umar said: Why may not a be appointed who should call (people) to prayer? The Messenger of Allah (ﷺ) said: O Bilal, get up and summon (the people) to prayer
Anas reported:Bilal was commanded (by the Messenger of Allah) to repeat (the phrases of) Adhan twice and once in Iqama. The narrator said: I made a mention of it before Ayyub who said: Except for saying: Qamat-is-Salat [the time for prayer has come]
Anas b. Malik reported:They (the Companions) discussed that they should know the timings of prayer by means of something recognized by all. Some of them said that fire should be lighted or a bell should be rung. But Bilal was ordered to repeat the phrases twice in Adhan, and once in Iqama
This hadith is transmitted by Khalid Hadhdha with the same chain of transmitters (and the words are):When the majority of the people discussed they should know, like the hadith narrated by al-Thaqafi (mentioned above) except for the words:" They (the people) should kindle fire
Abu Mahdhura said that the Messenger of Allah (ﷺ) taught him Adhan like this:Allah is the Greatest, Allah is the Greatest; I testify that there is no god but Allah, I testify that there is no god but Allah; I testify that Muhammad Is the Messenger of Allah, I testify that Muhammad is the Messenger of Allah, and it should be again repeated: I testify that there is no god but Allah, I testify that there is no god but Allah; I testify that Muhammad Is the Messenger of Allah, I testify that Muhammad is the Messenger of Allah. Come to the prayer (twice). Come to success (twice). Ishaq added: Allah is the Greatest, Allah is the Greatest; there Is no god but Allah
Hadis 843 — Sahih Muslim 4:7
حَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم مُؤَذِّنَانِ بِلاَلٌ وَابْنُ أُمِّ مَكْتُومٍ الأَعْمَى .
Ibn Umar reported:The Messenger of Allah (ﷺ) had two Mu'adhdhins, Bilal and 'Abdullah b. Umm Maktum, who (latter) was blind