Who is most entitled to lead the prayer?

The one who most deserves to lead the prayer is the one who
has most knowledge of the rulings on prayer and has memorized the most
Qur’aan. 

It was narrated that Abu Mas’ood al-Ansaari said: The
Messenger of Allaah (peace and blessings of Allaah be upon him) said:
“The people should be led in prayer by the one who has most knowledge of the
Book of Allaah; if they are equal in knowledge of the Qur’aan, then by the
one who has most knowledge of the Sunnah.” 

Narrated by Imam Muslim, 1530. 

What is meant by “the one who has most knowledge of the
Qur’aan” is not the one who can recite it most beautifully, but rather the
one who has memorized more of the Book of Allaah. This is indicated by the
hadeeth of ‘Amr ibn Salamah who said: “I used to memorize those words –
meaning the Qur’aan – and it was as if it took root in my heart. When Makkah
was conquered, then every tribe hastened to embrace Islam, and my father
urged our tribe to hasten to embrace Islam. When my father returned (from
the Prophet) to his tribe, he said, ‘By Allah, I have come to you from the
true Prophet (peace and blessings of Allaah be upon him)!’ The Prophet
(peace and blessings of Allaah be upon him) afterwards said to them,
‘Offer such-and-such a prayer at such-and-such a time, and when the time for
the prayer becomes due, then one of you should pronounce the Adhaan (for the
prayer), and let the one amongst you who knows most Qur’aan lead the
prayer.’ So they looked for such a person and found none who knew more
Qur’an than I, because of what I used to learn from the people. So they made
me their imam (to lead the prayer) and at that time I was a boy of six or
seven years.”

(Narrated by al-Bukhaari, 4051) 

We say that it is essential for the imam to know the rulings
on prayer, because he may do something, such as not breaking his wudoo’, or
missing out a rak’ah, and not know what to do about it, in which case he
would make a mistake and cause the prayer of others to be imperfect or
invalid altogether. 

Based on the hadeeth quoted above, some of the scholars said
that the one who has more knowledge of fiqh should lead the prayers. 

Al-Nawawi said: 

Maalik, al-Shaafa’i and their companions said that the one
who has more knowledge of fiqh should take precedence over the one who knows
more Qur’aan, because what he needs of recitation is known but what he needs
of fiqh may not be clear. There may arise during the prayer some matter
where only a person who has complete knowledge of fiqh will be able to know
the right thing to do. They said that this is the reason why the Prophet
(peace and blessings of Allaah be upon him) told Abu Bakr (may Allaah
be pleased with him) to lead the prayer rather than anyone else, even though
he (peace and blessings of Allaah be upon him) had stated that others
had more knowledge of Qur’aan than him. But some refuted this point by
quoting the hadeeth that said that the Sahaabah who had most knowledge of
Qur’aan were also those who had most knowledge of fiqh. But there is another
hadeeth according to which the Prophet (peace and blessings of Allaah
be upon him) said: “If they are equal in knowledge of Qur’aan, then the one
who has most knowledge of the Sunnah,” which indicates that those who have
most knowledge of Qur’aan should be given precedence in all cases. 

Sharh Muslim, 5/177 

Even though al-Nawawi differed with his imam al-Shaafa’i with
regard to the interpretation of the hadeeth, their words illustrate the
basic principle that there was no one among the Sahaabah who had a good
knowledge of the Qur’aan but was ignorant of the rulings of sharee’ah, as is
the case among many people nowadays. 

Ibn Qudaamah said: 

If one of them has more knowledge of the rulings on prayer,
and the other has more knowledge of matters other than prayer, then the one
who has more knowledge about prayer should be given precedence. 

Al-Mughni, 2/19 

The Standing Committee said: 

If this is understood, then it is not permissible for one who
is ignorant to lead the prayer unless he is leading others like him, if
there is no one who is better qualified to lead the prayer. 

Fataawa Islamiyyah, 1/264 

Secondly: 

We do not understand what is meant in the question. The
phrase “ill-Allaah” is not dhikr on its own, and it is not mentioned in any
dhikr on its own. Rather it comes as part of another phrase, namely Laa
ilaaha ill_Allaah wahdahu laa shareeka lah, lahu’l-mulk wa lahu’l-hamd was
huwa ‘ala kulli shay’in qadeer (There is no god but Allaah alone, with
no partner or associate; His is the Sovereignty and to Him be praise, and He
is able to do all things). And it appears in many other dhikrs.

 And Allaah knows best.