صَحِيحُ مُسْلِمٍ
Sahih Muslim 409 a
The Book of Prayers
Saying "Sami'a Allahu liman Hamidah," Rabbana wa lakal-hamd," and "Amin"
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ سُمَىٍّ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ إِذَا قَالَ الإِمَامُ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ . فَقُولُوا اللَّهُمَّ رَبَّنَا لَكَ الْحَمْدُ . فَإِنَّهُ مَنْ وَافَقَ قَوْلُهُ قَوْلَ الْمَلاَئِكَةِ غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ .
Abu Huraira reported: The Messenger of Allah (ﷺ) said: When the Imam says:" Allah listens to him who praises Him." you should say:" O Allah, our Lord for You is the praise." for if what anyone says synchronises with what the angels say, his past sins will be forgiven.
Sahih Muslim, 409 aSahihصحيح