Musnad Abu Ya'la al-Mawsili 243:4

Al-Abbas ibn al-Walid al-Narsi narrated to us, Yazid narrated to us, Sa'id narrated to us, Qatadah narrated to us, from Yunus ibn Jubayr, from Hattan ibn Abdullah al-Raqashi, that Abu Musa led them in prayer. When they sat at the end of their prayer, a man from the people said, "Prayer has been established with righteousness and zakat." When Abu Musa turned away [from the prayer], he faced the people and said, "Which of you said such-and-such a word?" The people remained silent twice. He said, "Perhaps you said it, O Hattan?" He replied, "I did not say it, and I feared that you would rebuke me for it." A man from the people said, "I said it, and I intended nothing by it but good." Abu Musa said, "Do you not know what you say in your prayer? The Prophet of Allah (peace and blessings of Allah be upon him) addressed us, explained our Sunnah to us, and taught us our prayer. He said: 'When you pray, straighten your rows, then let one of you lead you. When the Imam says the takbir, say the takbir. When he says, "Not of those who have earned Your anger, nor of those who have gone astray," say "Amin," and Allah will answer you. When he says the takbir and bows, say the takbir and bow, for the Imam bows before you and rises before you.' The Prophet of Allah (peace and blessings of Allah be upon him) said: 'That is for that.' 'When he says, "Allah hears those who praise Him," say, "O Allah, our Lord, to You be the praise," and Allah will hear you, for Allah has said upon the tongue of His Prophet: "Allah hears those who praise Him." When he says the takbir and prostrates, say the takbir and prostrate, for the Imam prostrates before you and rises before you.' The Prophet of Allah (peace and blessings of Allah be upon him) said: 'That is for that.' 'Until, when it is time for the sitting, let the first of what one of you says be: "The greetings, prayers, and good things are for Allah. Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous servants of Allah. I bear witness that there is no god but Allah, and that Muhammad is His servant and His messenger." Seven phrases of the prayer's greeting.'" Sa'id said: I do not know if that was in the statement of Abu Musa or something that Qatadah was saying, meaning his saying "seven phrases."