The words of the muezzin, “Prayer is better than sleep” (al-salaatu khayrun min al-nawm)

The Sunnah is to say these words in the second adhaan after
dawn has broken, as is narrated in the hadeeth of Abu Mahdhoorah and the
hadeeth of ‘Aa’ishah (may Allah be pleased with her), which indicate that
the muezzin used to say them in the second adhaan after dawn broke.
‘Aa’ishah said: Then the Prophet (blessings and peace of Allah be upon
him) would get up and pray two rak‘ahs, then he would go out to pray after
the first call, which was the second adhaan in relation to what is called
the first adhaan, and is the first adhaan with regard to the iqaamah,
because it may also be called “adhaan.” 

The Sunnah is to say these words in this adhaan which is the
second one after dawn has broken, and is the first in relation to the
iqaamah. With regard to the first adhaan, as people customarily call it,
this is to alert people. The Prophet (blessings and peace of Allah be upon
him) said concerning it: “So that those of you who are praying qiyaam can
rest and those of you who are sleeping can wake up.” This is the adhaan that
alerts people so that those who are asleep can wake up and those who are
praying qiyaam can rest, i.e., not make their prayers too long, because dawn
has come. In the hadeeth of ‘As’ishah, the later adhaan clearly called the
first adhaan in relation to the iqaamah, because the iqaamah is a second
adhaan, and the later adhaan may be called the second adhaan, in relation to
the first adhaan, the purpose of which is to alert people. 

Some of the scholars are of the view that these words should
be said in the first adhaan which serves to alert people before dawn breaks.
This issue is broad in scope, in sha Allah, but these words should not be
said in both calls. It is better to say them in the second call which is the
first in relation to the iqaamah and is the adhaan that is given after dawn
breaks. 

What is meant by the words “prayer is better than sleep” is
that the obligatory prayer that Allah has enjoined is better than sleep, and
what people should do is get up for it. With regard to the naafil prayers at
the end of the night or during the night, they are not obligatory, and sleep
may be better than prayer if being sleepy is going to affect his prayer. [In
that case] he should sleep and have his share of rest so that he will be
able to pray properly. But the obligatory prayer is something that is
required and is better than sleep in all cases; the individual has to get up
for it and do what will help him to perform the prayer mindfully and do it
well and properly. 

The one who hears this phrase should repeat it, “al-salaatu
khayrun min al-nawm (prayer is better than sleep)” because the Prophet
(blessings and peace of Allah be upon him) said: “When you hear the muezzin,
say what he says.” So the one who is responding should say “Al-salaatu
khayrun min al-nawm”, just as he repeats “Allahu akbar (Allah is most
great)” and “Ashhadu an la ilaaha ill-Allah (I bear witness that there is no
God but Allah)”; this is the same, he should say “al-salaatu khayrun min
al-nawm.” But when the muezzin says “Hayya ‘ala al-salaah, hayya ‘ala
al-falaah (come to prayer, come to prosperity)”, he should say, “Laa hawla
wa laa quwwata illa Billaah (there is no power and no strength except with
Allah).” This is what is prescribed. 

When the Prophet (blessings and peace of Allah be upon him)
heard the muezzin say “Hayya ‘ala al-salaah (come to prayer)”, he would say,
“Laa hawla wa laa quwwata illa Billah (there is no power and no strength
except with Allah).” When the muezzin says, “Hayya ‘ala al-falaah” say “La
hawla wa laa quwwata illa Billah,” because no one knows whether he will have
strength or not, or whether that will be easy for him or not, so he should
say Laa hawla wa laa quwwata illa Billaah, meaning I do not have the power
to respond to the muezzin and come to the mosque and perform the prayer
except by the help of Allah, may He be glorified and exalted; and I do not
have the strength to do that except by the help of Allah, may He be
glorified and exalted. The call of the muezzin is a call to good: “Hayya
‘ala al-salaah, hayya ‘ala al-falaah (Come to prayer, come to prosperity).”
So he has to respond and say, “Laa hawla wa laa quwwata illa Billah (There
is no power and no strength except with Allah).” This is what is prescribed,
meaning: I have no power or strength to respond to the muezzin or perform
the prayer on time with the congregation, or to do anything, except with the
help of Allah, may He be glorified and exalted. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)