Al-Kāfi - Volume 3 > Recitations in Salah (prayer)
Hadith #6

6ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ عُمَرَ بْنِ أُذَيْنَةَ وَابْنِ بُكَيْرٍ عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ الْسَّلام) قَالَ لاَ يُكْتَبُ مِنَ الْقِرَاءَةِ وَالدُّعَاءِ إِلاَّ مَا أَسْمَعَ نَفْسَهُ.

6. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from ‘Umar ibn ’Udhaynah and ibn Bukayr from Zurarah who has said the following: “Abu Ja’far, ‘Alayhi al-Salam, has said, ‘Of recitations and prayers, only such recitations and prayers are counted which one has made his own self to hear.’”