Muwatta Malik Book 5, Hadith 23
Yahya related to me from Malik from Jafar ibn Muhammad from his
father that the Messenger of Allah, may Allah bless him and grant him
peace, gave two khutbas on the day of jumua and sat down between them.
Yahya related to me from Malik that Safwan ibn Sulaym said, "If anyone omits jumua three times without reason or illness, Allah will set a seal on his heart." (Malik said, "I don't know if it was from the Messenger of Allah, may Allah bless him and grant him peace, or not.")
Yahya related to me from Malik from Ibn Shihab from Urwa ibn az- Zubayr from A'isha, the wife of the Prophet, may Allah bless him and grant him peace, that the Messenger of Allah, may Allah bless him and grant him peace, prayed in the mosque one night and people prayed behind him. Then he prayed the next night and there were more people. Then they gathered on the third or fourth night and the Messenger of Allah, may Allah bless him and grant him peace, did not come out to them. In the morning, he said, "I saw what you were doing and the only thing that prevented me from coming out to you was that I feared that it would become obligatory (fard) for you." This happened in Ramadan.