Al-Kāfi

Hadith 1205
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2ـ مُحَمَّدُ بْنُ إِسْمَاعِيلَ عَنِ الْفَضْلِ بْنِ شَاذَانَ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ جَمِيلِ بْنِ دَرَّاجٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) فَقُلْتُ مَا يَقُولُ الرَّجُلُ خَلْفَ الإِمَامِ إِذَا قَالَ سَمِعَ الله لِمَنْ حَمِدَهُ قَالَ يَقُولُ الْحَمْدُ لله رَبِّ الْعَالَمِينَ وَيَخْفِضُ مِنْ صَوْتِهِ.
2. Muhammad ibn ’Isma‘il has narrated from al-Fadl ibn Shadhan from Ibn Abi ‘Umayr from Jamil ibn Darraj who has said the following: “I once asked abu ‘Abd Allah (a.s.), about what one says when performing behind an Imam when he says, ‘Allah hears all those who praise him.’ He (the Imam) said that he must say, ‘All praise belong to Allah, Cherisher of the worlds’ and lowers his voice.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī