The congregation should not reply verbally to the azaan before the Jumu’ah khutbah. They may reply in their minds. However, the imaam may verbally reply to the azaan. He is also allowed to disapprove any incorrect action being carried out during the khutbah and if there is a genuine need, the imaam may even speak during the khutbah. ( Malfoozaat Of Faqeehul Ummah pg 239)
