ʿUyūn akhbār al-Riḍā

Hadith 248
congregational-prayer
248 - وَبِإِسْنادِهِ عَنْ عَلِيِ‏ عَلَيْهِ السَّلامُ، عَنِ النَّبِي‏صَلَّى اللهُ عَلَيْهِ وَآلِهِ قالَ: الإِثنانِ وَما فَوقَهُما جَماعَةٌ.
31-248 According to the same documentation, on the authority of Ali (a.s.), the Prophet (S) said, “Two or more make up a congregational prayer.”
Source: Shaykh Muḥammad b. ʿAlī al-Ṣaduq