It was narrated from Abu Hurairah that: The Messenger of Allah ( صلی اللہ علیہ وسلم ) said: "When the Imam says: 'Sami Allahu liman hamidah (Allah hears the one who praises Him),' then say: 'Rabbana wa lakal-hamd,' (Our Lord, and to You be the praise).' Whoever says that and it coincides with the angels saying it, his previous sins will be forgiven."

It was narrated from Hittan bin 'Abdullah that: He heard Abu Musa say: "The Prophet of Allah ( صلی اللہ علیہ وسلم ) 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 of Allah ( صلی اللہ علیہ وسلم ) 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 ( صلی اللہ علیہ وسلم ): "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 of Allah ( صلی اللہ علیہ وسلم ) 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.'"