It is not permissible to talk while the Imam is giving the Khutba

I have read a hadith that we can not talk to each other while the imam is giving khutba on friday.Last week i went to a mosque where a person was volentering (He was guiding people to go and sit in front and he was talking to them saying them salam and asking to sit them in front.m).Is it permissible?

Rulings on mosques |