Al-Kāfi

Hadith 1278
prayer-etiquette
3ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحَجَّالِ عَنْ ثَعْلَبَةَ بْنِ مَيْمُونٍ عَنْ يَحْيَى بْنِ طَلْحَةَ عَنْ سَوْرَةَ بْنِ كُلَيْبٍ قَالَ سَأَلْتُ أَبَا جَعْفَرٍ (عَلَيْهِ الْسَّلام) عَنْ أَدْنَى مَا يُجْزِئُ مِنَ التَّشَهُّدِ فَقَالَ الشَّهَادَتَانِ.
3. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from al-Hajjal, from Tha’labah ibn Maymun from Yahya ibn Talhah from Sawrah ibn Kulayb who has said the following: “I once asked abu Ja‘far (a.s.), about the minimum of what is sufficient for Tashahhud (testimonies of belief). He (the Imam) said, ‘It is the two testimonies of belief.”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī