Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.101.

It is preferred that he meet the following conditions:

1. It is a must that he make the azhan 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 azhan.

This hadith is related by Abu Dawud, an-Nasa’i, Ibn Majah and at-Tirmizhi, 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 azhan.

2. He should be clean from major or minor impurities. Al-Muhajir ibn Qanfazh reported that the Prophet, upon whom be peace, said to him, “Nothing prevented me from returning (your salutations) except that I dislike to mention the name of Allah when I am not clean. This report has come from Ahmad, Abu Dawud, an-Nasa’i, Ibn Majah and Ibn Khuzaimah. The latter grades it sahih.

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.

3. He should be standing and facing the qiblah (the direction of the Ka’bah). Said Ibn al-Munzhir, “There is agreement that it is sunnah for the caller to be standing, for then he can be heard far away. It is also sunnah that he face the qiblah while making the azhan. If he turns away from the qiblah, his azhan will be sound, but the act will be disliked.

4. He should turn with his head, neck and chest to the right upon saying “Hayya ‘alas-salah” and to the left upon saying Hayya ‘alalfalah.” Says an-Nawawi, “It is the most authentic form.”

Reported Abu Juhaifah, “Bilal made the azhan, 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.

5. He should insert his index fingers into his ears. Talking of his practice, Bilal said, “I put my index fingers into my ears and made the azhan. (Related by Abu Dawud and Ibn Hibban.)

Says at-Tirmizhi, “The scholars prefer the callers to put their index fingers into their ears while making the azhan.”

6. He should raise his voice for the call, even if he is alone in the desert. ‘Abdullah ibn ‘Abdurahman related from his father that Abu Sa’eed al-Khudri said to him, “I see that you love the sheep and the desert. If you are with your sheep or in the desert, then raise your voice while making the call to prayer, for any jinn, human or thing within hearing distance of your voice will be a witness for you on the Day of Resurrection…I heard the Messenger of Allah say that.” (Related by Ahmad, al-Bukhari, an-Nasa’i and Ibn Majah.)

7. He should pause between each phrase during the azhan and be quick in making the iqamah. Many narrations have reported that this act is preferred.

8. He should not speak during the iqamah. Some scholars dislike that he should even speak during the azhan, although al-Hasan, ‘Ata and Qatadah permit it. Says Abu Dawud, “I asked Ahmad, ‘May a man speak during his azhan?’ He said, ‘Yes.’ ‘May he speak during the iqamah?’ He said, ‘No,’ and that is because it is preferred that he make it quickly.”