Whether praying in congregation is Sunnah or obligation
31-12-2017 | IslamWeb
Question:
Assalaamu alaykum. The majority of the scholars say that praying in congregation is a highly-regarded action of the Sunnah, but that it is not obligatory. This means that though one misses the reward for attending the congregation, one is not sinful. Please mention the evidence based on which the majority based their opinion.
Answer:
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
Many scholars held that praying in congregation is an act of the Sunnah and not an obligation. This view was held preponderant by Ash-Shawkaani in his book Sharh Al-Muntaqa. One of their strongest pieces of evidence is the statement of the Prophet 
"Prayer in congregation is more virtuous than the prayer of an individual by twenty-seven degrees." [Al-Bukhaari and Muslim] The hadeeth assigns a virtue to the prayer of an individual, so it indicates that the one who prays individually is not sinful, though he misses the greater virtue of praying in congregation.
Al-Majmooʻ Sharh Al-Muhaththab maʻa Takmilat As-Subki wa Al-Muteeʻi reads:
"Our companions and the majority of the scholars held that performing the prayer in congregation is not an obligation required of each and every Muslim (man), as proven by the hadeeth reported on the authority of Ibn ʻUmar, who related that the Prophet said, 'Prayer in congregation is better than the prayer of a man by himself by twenty-seven degrees.' [Al-Bukhaari and Muslim] They (Al-Bukhaari and Muslim) also cited the version reported on the authority of Abu Hurayrah which reads 'by twenty-five degrees.' Al-Bukhaari also cited the hadeeth on the authority of Abu Saʻeed. The scholars underlined that such a comparison (between the reward of praying individually and in congregation) indicates that both actions are permissible and rewardable. Ash-Shawkaani said, '...and among their evidence that it is not obligatory is the following hadeeth: ‘If you have already prayed in your lodgings and then you come to a masjid in which there is a congregation, then pray with them, and it will be counted as a voluntary prayer for you.’ We have previously cited this hadeeth in the chapter on the legal concession of repeating the congregational prayer. They also brought forth as evidence the hadeeth reported on the authority of Abu Moosa in which the Messenger of Allah said, ‘The person who will receive the highest reward for the prayer is the one who comes from the farthest distance to perform it, then the one less distant, and the one who waits for the prayer to perform it with the imaam will have a greater reward than the one who performs it and then goes to sleep.’ [Al-Bukhaari and Muslim] In the narration of Abu Kurayb (the wording is), ‘The one who waits for the prayer until he prays it with the imaam in congregation.’ In addition, they relied on the fact that the Prophet, sallallahu ‘alayhi wa sallam, once commanded a delegation of new Muslims to observe the prayers, and he did not order them to perform it in congregation. It is established that it is not permissible (for the Prophet, sallallahu ‘alayhi wa sallam) to delay explanation past the time of need.'"
In fact, scholars had lengthy discussions regarding these two views. Ibn Al-Qayyim 
detailed this topic in his book As-Salah, supporting the view that it is obligatory to perform the prayer in congregation, and he refuted the evidence supporting the opposing opinion, so please refer to it.
For more benefit, please refer to fatwa 337036.
Allah knows best.