Salam aleikum, Why are there three adhans for the fajr prayer? I find it very confusing. Is there any proof for this habit in a hadith?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The confirmed Sunnah from the Prophet about Fajr is that it has two Athaans (call to the prayer): the first Athaan is called a short while before the beginning of the real time of Fajr, so that a sleeping person would wake up, and the one who is performing night prayer would end his prayer and come back for a short rest before Fajr, or in order to have Sahoor [the predawn meal] for whoever wants to fast. The second Athaan is called precisely at the beginning time of Fajr.

There are many Prophetic narrations which prove this. For instance, Ibn 'Umar narrated: "I heard the Prophet saying: ‘‘Bilaal  calls the Athaan when it is still night, so eat and drink until you hear the Athaan of Ibn Umm Maktoom." [Al-Bukhari and Muslim] The second evidence is that Ibn Mas’ood narrated that the Prophet said: ‘‘The Athaan given by Bilaal should not prevent anyone of you from having his Sahoor, as he calls when it is still night so that a person who is performing the night prayer would end his prayer, and so that the sleeping person would wake up." [Al-Bukhari and Muslim]

However, we do not know any evidence from the Sunnah about the existence of the third Athaan for the Fajr prayer, except the Iqaamah, which is also called the Athaan.

Nonetheless, the jurists stated that it is permissible to call many Athaans by many Mu’aththins (person who calls the Athaan) in one mosque when there is a need for it, but this is not restricted to the Fajr Athaan.

Moreover, Ibn Hajar said: “If there is a need for having many Mu’aththins because of the distance between the areas of a given town, then each one should call the Athaan in a given direction and they should not all do so at the same time.”

For more benefit, please refer to Fatwa 91205.

Allaah Knows best.