Excellence of Replying to Azan
The Holy Prophet صلى الله علیہ وسلم once said, “O women! Whenever you hear Bilal uttering Azan and Iqamat, you should also say what he says as Allah عزوجل will write one hundred thousand good deeds for you for every Kalimah, raise your one thousand ranks and will remove your one thousand sins.” Listening to this, the women asked, “This (Sawab) is for women; what is for men?” The beloved and blessed Prophet صلى الله علیہ وسلم replied, “There is double (Sawab) for men.”
(Tarikh-e-Dimshq la bin Asakir, pp. 75, vol, 55)
Earn 30 Milion and 24 Hundred Thousand Good Deeds
The Muazzin should utter the Kalimat of Azan with pauses. اللهُ اكبراللهُ اكبر ( when uttered together without a pause ) are considered one Kalimah. After uttering this, he should take a pause for the amount of time in which the replier can reply. Not taking the pause is Makruh and therefore, repeating such Azan is Mustahab. (Dur-re-Mukhtar, pp. 66, vol. 2, Rad-dul-Muhtar, pp. 66, vol. 2 ) The replier should say اللهُ اكبراللهُ اكبر during the pause of the Muazzin, i.e. when the Muazzin is silent. He should reply to the other Kalimat in the same way. When the Muazzin says 
the first time, the replier should say:
May Allah’s Durud upon you Ya Rasulallah صلى الله علیہ وسلم!
When the Muazzin utters these words again, the replier should say:
Ya Rasulallah صلى الله علیہ وسلم! You are the solace of my eyes,
Each time, make thumb nails touch eyes and say:
Ya Allah عز وجل! Benefit me from my faculties of listening and seeing.
Whoever does this, the Holy Prophet صلى الله علیہ وسلم will make him enter Heaven accompanying him. (Rad-dul-Muhtar, pp. 84, vol. 2 )
In reply to 
and 
say 
each time, and it is better to say both ( what the Muazzin says as well as 
) and also add:
Whatever Allah عز وجل wanted happened and whatever He did not want did not happen.
( Dur-re-Mukhtar-o-Rad-dul-Muhtar, pp. 82, vol. 2 ) ( Fatawa-e-Alamgiri, pp. 57, vol. 1 )
In reply to 
, say:
You are true and pious and have said right.
( Dur-re-Mukhtar-o-Rad-dul-Muhtar, pp. 83, vol. 2 )
Replying to Iqamat is Mustahab. Its reply is similar to that of Azan. The only difference is that in reply to 
the replier should say:
May Allah عز وجل persist it until sky and earth exist!
( Bahar-e-Shariat, pp. 473, vol. 1 ) ( Fatawa-e-Alamgiri, pp. 57, vol. 1 )
{ Laws of Salah (Hanafi) Page 80 to 82 }
Nine Madani Pearls about Replying to Azan
In addition to the Azan of Salah, other Azan such as the one uttered at the time of the birth of a baby should also be replied. (Rud-dul-Muhtar, pp. 82, vol. 2)
- Muqtadis should never reply to the Azan of Khutbah. If is most cautious to refrain in this case. However, there is no harm if the reply the Azan or supplication (between two Khutbat) is made in heart without uttering any word with the tongue. However, if the Imam replies to the Azan or makes supplication even with the tongue, it is quite permissible. (Fatawa Radawiyyah (Jad id), pp. 300, 301, vil. 8)
- There is a commandment to reply for the hearer of Azan. (Fatawa-e-‘Alamgiri, pp. 57, vol. 1) A Junub (the one who is to do Ghusl because of intercourse or nocturnal emission) should also reply to Azan. However, a woman undergoing menses or post-natal bleeding, audience of Khutbah, performers of funeral Salah, those having intercourse or those passing stool or urine need not to reply. (Dur-re-Mukhtar, pp. 81, vol. 2)
- When Azan is going on, one should stop every type of work such as talking, Salam, reply to Salam and even recitation of the Holy Quran etc. for the duration in which Azan is being uttered. Listen to the Azan attentively and make its reply. Do also the same while Iqamat is going on. (Bahar-e-Shariat, pp. 473, vol. 1, Dur-re-Mukhtar pp. 86, 87, vil. 2, ‘Alamgiri, pp. 57, vol. 1)
- It is safer to stop walking, eating, picking or laying a utensil or other things, playing with children, talking by gestures etc. diring Azan.
- The one talking during Azan is in the danger of losing faith at the time of death. (Bahar-r-Shariat, pp. 473, vol. 1)
- If anybody hears the Azan while walking, it is better for him to stop walking and remain silent for the amount of time in which Azan is uttered and reply to the Azan. (Fatawa-e-‘Alamgiri, pp. 57, vol. 1, Bahar-r-Shariat pp. 473, vol. 1)
- If anybody hears more than one Azan, he is required to reply to the first Azan only but it is better to reply to all of them. (Dur-re-Mukhtar-o-Rad-dul-Muhtar, pp. 82, vol. 2)
If anybody did not reply during the Azan and much time has not passed yet, he should still reply. (Dur-re-Mukhtar, pp. 83, vil. 2)
Seven Madani Pearls about Iqamat
- It is better to say Iqamat just behind the Imam in the Masjid; if it is not conveniently possible to utter Iqamat just behind the Imam, then it should be uttered at the right side. (Fatawa Radawiyyah (Jad id), pp. 372, vol. 5)
- Iqamat is a more emphatic Sunnah than Azan. (Rad-dul-Muhtar, pp. 67, vol. 2)
- It is Mustahab to reply to Iqamat. (Fatawa-e-‘Alamgiri, pp. 57, vol. 1)
- Say the words of Iqamat quickly without pauses in between. (Bahar-e-Shariat, pp. 470, vol. 1)
- Turn face to the right and left side whilst saying
and respectively during Iqamat as well. (Dur-re-Mukhtar, pp. 6.66, vol. 2) - Iqamat is the right of the person who uttered Azan. However, with the consent of the utterer of Azan, someone else can also say Iqamat. If the Iqamat is uttered without the permission of the Muazzin (the one who uttered Azan) and he resented it, then it is Makruh. (Fatawa-e-‘Alamgiri, pp. 54, vol. 1)
- If a person comes during Iqamat, it is Makruh for him to wait whilst standing, instead, he should sit down. Similarly, the people who are already sitting in the Masjid should also keep seated; all should stand when the Mukabbir says . This ruling also applies to the Imam. (Fatawa-e-‘Alamgiri, pp. 57, vol. 1, Bahar-r-Shariat, pp. 471, vol. 1)
{Laws of Salah (Hanafi) Page 84 to 86}