«إنما جعل الإمام جنة فإذا صلى قاعدا فصلوا قعودا وإذا قال سمع الله لمن حمده فقولوا: اللهم ربنا لك الحمد فإذا وافق قول أهل الأرض قول أهل السماء غفر له ما تقدم من ذنبه»
The Prophet (peace and blessings be upon him) said:
"The imam has been made a shield (as it were). So when he prays sitting, all of you pray sitting; and when he says 'Sami'a Allahu liman hamidah' (Allah hears the one who praises Him), then say 'Allahumma rabbana lakal-hamd' (O Allah, our Lord, to You belongs all praise). For when the words of the people of the earth coincide with the words of the people of the heavens (the angels) (at that moment), his (the follower's) previous sins are forgiven."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 2355