Maliks Muwatta Book 5, Hadith Number 23.
Section : The Recitation in the Jumua Prayer, the Sitting, and Missing the Prayer Without a Reason.
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.