Al-Kāfi - Volume 3 > Recitations in Salah (prayer)
Hadith #16

16ـ أَحْمَدُ بْنُ إِدْرِيسَ عَنْ مُحَمَّدِ بْنِ أَحْمَدَ عَنْ يَعْقُوبَ بْنِ يَزِيدَ عَنْ مُحَمَّدِ بْنِ أَبِي حَمْزَةَ عَمَّنْ ذَكَرَهُ قَالَ قَالَ أَبُو عَبْدِ الله (عَلَيْهِ الْسَّلام) يُجْزِئُكَ مِنَ الْقِرَاءَةِ مَعَهُمْ مِثْلُ حَدِيثِ النَّفْسِ.

16. Ahmad ibn Idris has narrated from Muhammad ibn Ahmad from Ya’qub ibn Yazid from Muhammad ibn abu Hamzah from those whom he has mentioned who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘When performing Salah (prayer) with them (other people) it is sufficient to recite like speaking to one’s soul.’”