Is it disliked to repeat the congregational prayer in a mosque that already has a regular Imam?
Chapter on Imamate and Congregational Prayer
Al-Mughni
Book of Prayer
Primary text
Repeating the congregational prayer in a mosque with a regular Imam is not disliked by some, including Ibn Mas'ud, 'Ata, Al-Hasan, An-Nakha'i, Qatadah, and Ishaq. The general ruling permits it to secure the virtue of congregational prayer, which surpasses individual prayer by twenty-five or twenty-seven degrees, based on the general saying of the Prophet, peace be upon him. Evidence supports this through the narration where a man came after the Prophet had prayed, and someone stood up to pray with him, implying the validity of a second prayer group, with Al-Tirmidhi grading the narration as Hasan.
Supporting text
The majority opinion, held by Salm, Abu Qilabah, Ayyub, Ibn 'Awn, Al-Layth, Al-Bitti, Ath-Thawri, Malik, Abu Hanifah, Al-Awza'i, and Ash-Shafi'i, holds that repeating the congregation is not to be done in a mosque with a regular Imam, unless it is in a thoroughfare, to prevent discord and negligence regarding the established Imam. They liken it to the mosque of the Prophet, peace be upon him, where repetition was disliked.