كتاب الصلاة
4  
Prayer
(13a)
Chapter: What is Recited During the Prayer - Section 1
(12)
باب القراءة في الصلاة - الفصل الأول
Mishkat al-Masabih 825
Abu Huraira reported God’s Messenger as saying, “Say Amen when the imam says it, for if anyone’s utterance of Amen synchronises with that of the angels, he will be forgiven his past sins. ’ (Bukhari and Muslim.) In a version he said, “When the imam says, ‘Not of those with whom Thou art angry nor of those who go astray’, say Amen, for if anyone’s words synchronise with those of the angels he will be forgiven his past sins.” This is Bukhari’s wording, and Muslim has something similar. In another version by Bukhari he said, “Say Amen when the reciter (i.e. the imam) says it, for the angels do so, and if anyone’s utterance of Amen synchronises with that of the angels, he will be forgiven his past sins.”
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " إِذَا أَمَّنَ الْإِمَامُ فَأَمِّنُوا فَإِنَّهُ مَنْ وَافَقَ تَأْمِينُهُ تَأْمِينَ الْمَلَائِكَةِ غُفِرَ لَهُ مَا تقدم من ذَنبه) وَفِي رِوَايَةٍ قَالَ: " إِذَا قَالَ الْإِمَامُ: (غَيْرِ المغضوب عَلَيْهِم وَلَا الضَّالّين) فَقُولُوا: آمِينَ فَإِنَّهُ مَنْ وَافَقَ قَوْلُهُ قَوْلَ الْمَلَائِكَةِ غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ ". هَذَا لَفْظُ الْبُخَارِيِّ وَلِمُسْلِمٍ نَحْوُهُ وَفِي أُخْرَى لِلْبُخَارِيِّ قَالَ: «إِذَا أَمَّنَ الْقَارِئُ فَأَمِّنُوا فَإِنَّ الْمَلَائِكَةَ تُؤَمِّنُ فَمَنْ وَافَقَ تَأْمِينُهُ تَأْمِينَ الْمَلَائِكَةِ غفر لَهُ مَا تقدم من ذَنبه»
  مُتَّفَقٌ عَلَيْهِ   (الألباني) حكم   :
Reference : Mishkat al-Masabih 825
In-book reference : Book 4, Hadith 252