Narrated AbuMusa al-Ash'ari:
Hittan ibn Abdullah ar-Ruqashi said: AbuMusa al-Ash'ari led us in
prayer.
When he sat at the end of his prayer, one of the people said: Prayer
has been established by virtue and purity.
When AbuMusa returned (from his prayer or finished his prayer), he
gave his attention to the people, and said: Which of you is the
speaker of such and such words? The people remained silent. Which of
you is the speaker of such and such words? The people remained
silent. He said: You might have said them, Hittan. He replied: I did
not say them. I was afraid you might punish me. One of the people
said: I said them and I did not intend by them (anything) except
good.
AbuMusa said: Do you not know how you utter (them) in your prayer?
The Apostle of Allah (peace_be_upon_him) addressed us, and taught us
and explained to us our way of doing and taught us our prayer.
He said: When you pray a (congregational) prayer, straighten your
rows, then one of you should lead you in prayer. When he says the
takbir (Allah is Most Great), say the takbir, and when he recites
verses "Not of those upon whom is Thy anger, nor of those who err"
(i.e. the end of Surah i.), say Amin; Allah will favour you. When he
says "Allah is most great," and bows, say "Allah is most great" and
bow, for the imam will bow before you, and will raise (his head)
before you.
The Apostle of Allah (peace_be_upon_him) said: This is for that.
When he says "Allah listens to the one who praises Him," say: "O
Allah, our Lord, to Thee be praise, Allah be praised," Allah will
listen to you, for Allah, the Exalted, said by the tongue of His
Prophet (peace_be_upon_him): "Allah listens to the one who praises
Him." When he says "Allah is most great" and prostrates, say: "Allah
is most great" and prostrate, for the imam prostrates before you and
raises his head before you.
The Apostle of Allah (peace_be_upon_him) said: This is for that.
When he sits, each one of you should say "The adorations of the
tongue, all good things, and acts of worship are due to Allah. Peace
be upon you, O Prophet, and Allah's mercy and His blessings. Peace
be upon us and upon Allah's upright servants. I testify that there
is no god but Allah, and I testify that Muhammad is His servant and
Apostle."