Is it permissible to perform voluntary prayers in congregation or individually?

Primary text

Voluntary prayers are permissible both individually and in congregation. The Prophet, peace be upon him, performed both methods. His solitary prayers were more frequent. He prayed in congregation once with Hudhayfah, once with Ibn Abbas, once with Anas, his mother, and the orphan, once leading his companions in the house of Uthban, and led them in prayer during three nights of Ramadan. These actions establish the permissibility of both modes for voluntary worship.