Sunan an-Nasa’i: Book 12, Hadith 144

It was narrated from Hittan bin ‘Abdullah that Al-Ash’ari said: “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 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 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).”