Sahih Muslim 404 a

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 Messenger of Allah (ﷺ) 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 Your 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 Messenger of Allah (ﷺ) said: This is for that. When he says "Allah listens to the one who praises Him," say: "O Allah, our Lord, to You be praise, Allah be praised," Allah will listen to you, for Allah, the Exalted, said by the tongue of His Prophet (ﷺ): "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 Messenger of Allah (ﷺ) 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 Messenger." This version of Ahmad does not mention the words "and His blessings" nor the phrase "and I testify"; instead, it has the words "that Muhammad."

"Abu Musa led us in prayer and when he was sitting, a man from among the people entered and said: 'Prayer is based on righteousness and is always mentioned alongside Zakah (in the Qur'an).' When Abu Musa had said the Salam, he turned to the people and said: 'Which of you spoke these words?' The people kept quiet. Then he said: 'O Hittan, perhaps you said it?' He said: 'No, but I was afraid that you would rebuke me for it.' He said: 'The Messenger of Allah (ﷺ) taught us our prayer and Sunnah prayers, and he said: The Imam is appointed to be followed, so when he says the Takbir, say the Takbir; when he says "Not (the way) of those who earned Your Anger, nor of those who went astray," say Amin, and Allah will respond to you; when he rises up from bowing and says, 'Sami' Allalhu liman hamidah (Allah hears those who praise Him), say 'Rabbana lakal-hamd (Our Lord, to You be praise),' and Allah will hear you; when he prostrates, prostrate, and when he sits up, sit up. The Imam should prostrate before you do and sit up before you do.' The Messenger of Allah (ﷺ) said: 'This makes up for that.'"

He heard Abu Musa say: "The Prophet (ﷺ) of Allah (ﷺ) addressed us and taught us our Sunnah and our prayer. He said: 'When you pray, make your rows straight and let one of you lead you in prayer. When the Imam says the takbir, then say the takbir. When he recites 'Not (the way) of those who earned Your anger, nor those who went astray' then say: "Amin" and Allah will answer you. When he says the takbir and bows, then say the takbir and bow. The Imam bows before you do and stands up before you do.' The Prophet (ﷺ) of Allah (ﷺ) said: 'This makes up for that. And when he says: "'Sami Allahu liman hamidah (Allah hears the one who praises Him),' then say: "Allahumma Rabbana wa lakal-hamd (O Allah, our Lord, and to You be the praise), " Allah will hear you, for Allah has said on the lips of His Prophet (ﷺ): "Allah hears the one who praises Him." And when he (the Imam) says the takbir and prostrates, then say the takbir and prostrate. The Imam prostrates before you do and sits up before you do.' The Prophet (ﷺ) of Allah (ﷺ) said: 'This makes up for that. And when he is sitting, let the first thing that any one of you says be: At-tahiyaatut-tayyibatus-salawatuLillah, salamun 'alayka ayyuhanabiyyu wa rahmatullahi wa barakatuhu, salamun 'alayna wa 'ala 'ibadillahis-salihin, ashhadu an la ilaha ill-Allah wa ashhadu anna Muhammadan 'abduhu wa rasuluh (All compliments, good words and prayers are due to Allah, peace be upon you O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous slaves of Allah. I bear witness that there is none worthy of worship except Allah and I bear witness that Muhammad is His slave and Messenger)- seven phrases which are the greeting of the prayer.'"

"The Messenger of Allah (ﷺ) addressed us and taught us our Sunnahs and our prayer. He said: 'Make your rows straight, then let one of you lead the others. When he says the takbir, then say the takbir; when he says: "Wa lad-dallin" then say "Amin" and Allah (SWT) will answer you. When the Imam says the takbir and bows, then say the takbir and bow, for the Imam bows before you and stands up before you.' The Prophet (ﷺ) of Allah (ﷺ) said: 'This makes up for that. When he says: 'Sami Allahu liman hamidah (Allah hears the one who praises Him), say: "Rabbana wa lakal-hamd (Our Lord, to You be praise)," Allah (SWT) will hear you, for indeed Allah, the Mighty and Sublime, has said on the tongue of His Prophet (ﷺ): "Allah hears the one who praises Him." Then when the Imam says the takbir and prostrates, say the takbir and prostrate, for the Imam prostrates before you and rises before you.' The Prophet (ﷺ) of Allah (ﷺ) said: 'This makes up for that. Then when you are sitting, let the first thing that any one of you says be: At-tahiyyatu lillahi was-salawatu wat-tayyibat, as-salamu 'alaika ayyuhan-Nabiyyu wa rahmatAllahi wa baraktuhu. As-salamu 'alaina wa 'ala 'ibad illahis-salihin, ashahdu an la illaha ill-Allah wa ashhadu anna Muhammadan 'abduhu wa rasuluhu (Allah compliments, prayers and pure words are due to Allah. Peace be upon you, O Prophet, and the mercy of Allah (SWT) and his blessings. Peace be upon us and upon the righteous slaves of Allah (SWT). I bear witness that none has the right to be worshipped except Allah and I bear witness that Muhammad is His slave and Messenger)."

"The Messenger of Allah (ﷺ) addressed us and taught us our Sunnahs and our prayer. He said: 'When you stand for the prayer, make your rows straight, then let one of you lead the others. When he says the takbir, then say the takbir; when he says : "Wa lad-dallin" then say "Amin" and Allah (SWT) will answer you. Then when he says the takbir and bows, then say the takbir and bow, for the Imam bows before you and stands up before you.' The Prophet (ﷺ) of Allah (ﷺ) said: "This makes up for that. When he says: 'Sami' Allahu liman hamidah (Allah hears the one who praises Him),' say: 'Allahumma, Rabbana wa lakal-hamd (O Allah, our Lord, to You be praise),' Allah will hear you, for indeed Allah (SWT), the Mighty and Sublime, has said on the tongue of His Prophet: "Allah hears the one who praises Him." Then when he says the takbir and prostrates, say the takbir and prostrate, for the Imam prostrates before you and rises before you.' The Prophet (ﷺ) of Allah (ﷺ) said: 'This makes up for that. Then when you are sitting, let the following be among what one of you says: At-tahiyyatu lillahi wasalawatu wat-tayibaat, as-salamu 'alaika ayah-Nabiyyu wa rahmatAllahi wa baraktuhu. As-salamu 'alaina a 'ala ibad illahis-salihin, ashadu an la ilaha ill Allah, wa ashhadu anna Muhammadan 'abduhu wa rasuluhu. (All compliments, prayers and pure words are due to Allah. Peace be upon you O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous slaves of Allah. I bear witness that that none has the right to be worshipped except Allah, and I bear witness that Muhammad is His slave and messenger.)"