Maliks Muwatta Book 005, Hadith Number 006.

Section : Paying Attention when the Imam is Giving the Khutba on the Day of Jumua.

Yahya related to me from Malik from Abu'z Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "Even saying to your companion 'Listen' while the imam is giving the khutba on the day of jumua, is to speak foolishly."