Fiqh-us-Sunnah - 1.101

Hadith 1.101.1

Conditions to be met by the caller to prayer

It is preferred that he meet the following conditions: It is a must that he make the adhan for Allah's sake and not for wages. 'Uthman ibn Abu al-'Aas asked the Messenger of Allah, upon whom be peace, to appoint him as the imam of his people. He replied, "You are their imam. Be careful about the weak amongst them, and appoint a caller to prayer who does not accept wages for his adhan.
This hadith is related by Abu Dawud, an-Nasa'i, Ibn Majah and at-Tirmidhi, with a slightly different wording, who called it hasan. He also said that the scholars agree with this, and that they hate to see the caller receive wages for the adhan.
According to the Shafiyyah, making the call while one is not in a state of cleanliness is permissible although disliked. According to Ahmad, the Hanafiyyah and others, it is permissible and is not disliked.
Reported Abu Juhaifah, "Bilal made the adhan, and I saw the movement of his mouth from this side to that side upon saying "Hayya 'alas-salah" and "Hayya 'alal-falah."
(Related by Ahmad, al-Bukhari and Muslim.) According to al-Baihaqi, this turning is not documented through sound chains. In al-Mughni, it states from Ahmad that the caller should not turn to the left or to the right unless he is at the top of a minaret, so that the people on both sides can hear him.
Says at-Tirmidhi, "The scholars prefer the callers to put their index fingers into their ears while making the adhan."