There is no particular saheeh (authentic) text which speaks of the virtues of Surah al-Jumu’ah, rather it was narrated that the Prophet (peace and blessings of Allah be upon him) used to recite it in the first rak’ah (unit) of the Jumu’ah prayer. It was narrated from Ibn ‘Abbas (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) used to recite al-Jumu’ah and al-Munafiqoon in the Jumu’ah prayer. Narrated by Muslim (879).
It says in al-Saheeh wa’l-Saqeem min Fadail al-Quran al-Kareem by Amal Sa’di (p.81): There is no saheeh report from the Messenger of Allah (peace and blessings of Allah be upon him) about the virtues of Surah al-Jumu’ah. There are da’eef (weak) and mawdoo’ (fabricated) reports about its virtues, such as, “The one who recites Surah al-Jumu’ah will be given hasanat (good) in reward equal to the number of those who come to Jumu’ah and those who do not in the Muslim regions” – narrated by al-Tha’labi in al-Kashf wa’l-Bayan (9/305), via Abu ‘Asmah ibn Abi Maryam, the well known fabricator and liar. Hence al-Manawi said in al-Fath al-Samawi: it is mawdoo’. End quote.
But Surah al-Jumu’ah is one of the mufassal surahs (those in the latter part of the Quran) which the Prophet (peace and blessings of Allah be upon him) said he was favoured with above all other Books and Prophets. It was narrated from Wathilah ibn al-Asqa’ that the Prophet (peace and blessings of Allah be upon him) said: “I have been favoured with al-Mufassal.”
Narrated by Ahmad (4/107); classed as saheeh by al-Albani in Bidayat al-Sool, p.59. He said: The reviewers of al-Musnad under the supervision of al-Shaykh Shu’ayb al-Arnaoot said that its isnad (chain of transmission) is hasan (good).
And Allah knows best.