Al-Kāfi

Hadith 1654
friday-prayercongregational-prayer
4ـ عَلِيٌّ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنِ ابْنِ أُذَيْنَةَ عَنْ زُرَارَةَ قَالَ كَانَ أَبُو جَعْفَرٍ (عَلَيْهِ الْسَّلام) يَقُولُ لاَ تَكُونُ الْخُطْبَةُ وَالْجُمُعَةُ وَصَلاَةُ رَكْعَتَيْنِ عَلَى أَقَلَّ مِنْ خَمْسَةِ رَهْطٍ الإِمَامِ وَأَرْبَعَةٍ.
4. Ali has narrated from his father from Ibn Abi ‘Umayr from ibn ’Udhaynah from Zurarah who has said the following: “Abu Ja‘far (a.s.), has said, ‘The sermons and Friday Salah (prayer) are not valid without the presence of five people, the fifth of whom is the Imam.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī