Sahih al-Bukhari
Sahih al-Bukhari 658
Two or more than two persons are considered as a group (for the congregational prayers)
Arabic hadith text
حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ أَبِي قِلاَبَةَ، عَنْ مَالِكِ بْنِ الْحُوَيْرِثِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ "إِذَا حَضَرَتِ الصَّلاَةُ فَأَذِّنَا وَأَقِيمَا، ثُمَّ لِيَؤُمَّكُمَا أَكْبَرُكُمَا "
Translation
Narrated Malik bin Huwairith
Prophet said (to two persons), "Whenever the prayer time becomes due, you should pronounce Adhan and then Iqama and the older of you should lead the prayer."