Al-Kāfi

Hadith 1294
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8ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنْ فَضَالَةَ بْنِ أَيُّوبَ عَنْ أَبَانٍ عَنْ إِسْمَاعِيلَ بْنِ الْفَضْلِ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنِ الْقُنُوتِ وَمَا يُقَالُ فِيهِ فَقَالَ مَا قَضَى الله عَلَى لِسَانِكَ وَلاَ أَعْلَمُ لَهُ شَيْئاً مُوَقَّتاً.
8. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from al-Husayn ibn Sa‘id from Fadalah ibn Ayyub from Aban ibn ’Isma‘il ibn al-Fadl who has said the following: “I once asked abu ’Abd Allah (a.s.), about Qunut (supplication after recitation in second Rak‘at) and what is said in it. He (the Imam) said, ‘Say whatever Allah makes to come out from your tongue. I do not know of anything definite for it.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī