Can You Pray Sunnah in Congregation?
Question

Is it permissible to offer Nafl prayers in congregation, such as Qiyam Al-layl or Duha prayer?
Praise be to Allah.There is nothing wrong with offering Nafl (supererogatory) prayers in congregation, but that should not be done on an ongoing basis, rather it may only be done sometimes. 
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 
“Voluntary prayers done in congregation are of two types, one of which it is Sunnah to do in congregation, such as the eclipse prayer, prayers for rain, and Qiyam during Ramadan (Tarawih) . These are always done in congregation as is the Sunnah. 
The second type is not done in congregation, such as Qiyam Al-layl , the regular Sunnah prayers, Duha prayer , Tahiyyat Al-Masjid (greeting the mosque) and so on. But if they are done in congregation occasionally, that is permissible. 
As for doing them in congregation on an ongoing basis, that is not prescribed, rather it is a reprehensible innovation. The Prophet (peace and blessings of Allah be upon him) and the Companions and Followers were not accustomed to offering Nafl prayers in congregation. 
The Prophet (peace and blessings of Allah be upon him) only rarely offered voluntary prayers in congregation. He used to pray qiyam Al-layl on his own, but when Ibn 'Abbas (may Allah be pleased with him) stayed overnight with him, he prayed with him. 
On another occasion, Hudhayfah (may Allah be pleased with him) prayed with him, and on another occasion Ibn Mas`ud (may Allah be pleased with him) prayed with him. Similarly he (peace and blessings of Allah be upon him) also prayed at the house of `Utban ibn Malik Al-Ansari, in a place that he (`Utban) took as a prayer place for himself, so he prayed with him, and he also led Anas and his mother and the orphan in prayer, but in general his voluntary prayers were offered alone.” (Majmu` Al-Fatawa, 23/414) 
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) was asked: What is the ruling on offering Nafl prayers in congregation, such as Duha prayer? 
He replied: 
“There is nothing wrong with offering Nafl prayers in congregation occasionally, because the Prophet (peace and blessings of Allah be upon him) led his companions in Nafl prayers on some nights. On one occasion ‘Abdullah ibn `Abbas (may Allah be pleased with him) prayed with him, and on another occasion `Abdullah ibn Mas`ud (may Allah be pleased with him) prayed with him, and on one occasion Hudhayfah ibn Al-Yaman (may Allah be pleased with him) prayed with him. Hudhayfah narrated that the Prophet (peace and blessings of Allah be upon him) recited Al-Baqarah, An-Nisa’ and Al `Imran, and he did not reach a verse that spoke of seeking refuge with Allah but he sought refuge with Him, and he did not reach a verse that spoke of mercy but he asked for mercy. ‘Abdullah ibn Mas`ud prayed with the Prophet (peace and blessings of Allah be upon him) one night, and the Prophet (peace and blessings of Allah be upon him) stood for a long time; `Abdullah ibn Mas`ud said: Until I thought of something bad. It was said: What is the bad thing that you thought of? He said: Sitting down and leaving him – that was because he (peace and blessings of Allah be upon him) stood for such a long time. `Abdullah ibn `Abbas (may Allah be pleased with him) stood and prayed with the Prophet (peace and blessings of Allah be upon him) one night, standing on his left, and the Prophet (peace and blessings of Allah be upon him) took hold of his head and made him stand on his right. 
In conclusion, there is nothing wrong in offering some Nafl prayers in congregation, but this should not be a regular habit such that every regular Sunnah prayer is offered in congregation, because that is not prescribed.” (Majmu` Fatawa Ibn `Uthaymin, 14/334)
And Allah knows best.