Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَ سَأَلَ اَلْحَسَنُ اَلصَّيْقَلُ أَبَا عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ: عَنْ أَقَلِّ مَا تَكُونُ اَلْجَمَاعَةُ قَالَ «رَجُلٌ وَ اِمْرَأَةٌ.
Al-Hasan al-Sayqal asked Imam Jafar ibn Muhammad Al-Sadiq عليه السلام about the minimum number for a congregation. Imam عليه السلام said: "A man and a woman."
- Ṣaḥīḥ al-Faqīh, p. 52