Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.133.

Section : The number of people required for al-Jumu’ah.

There is no dispute among the scholars that a congregation is a necessary condition for the validity of al-Jumu’ah. This is based on the hadith of Tariq ibn Shihab who reports that the Prophet said: “Al-Jumu ‘ah is an obligation (wajib) upon every Muslim in the community.” However, the scholars do differ on how many people are required for al-Jumu’ah. There are fifteen different opinions on this question and they are mentioned by Ibn Hajar in Fath al-Bari. The strongest opinion is that salatul Jumu’ah is valid if there are two or more people present since the Prophet is reported to have said: “Two or more constitute a congregation.”

Ash-Shaukani says: ‘The other prayers are considered to be made in congregation if there are two people present. The same applies to Jumu’ah salah, unless there is a reason for it to be different. There is no evidence to show that [for the purpose of the congregation] its number should be larger than that for the other prayers. ‘Abdul Haqq says: ‘There is no confirmed hadith on the number of people needed for al-Jumu’ah.’ Similarly, as-Sayuti holds: ‘There is no confirmed hadith which states a particular number [for the Jumu’ah salah].'” This is also the opinion of at-Tabari, Dawud, an-Nakha’i, and Ibn Hazm.