Listening to the khutbah: adab and reward
The Prophet ﷺ emphasized silence so strongly that even telling someone to be quiet counts as idle talk:
"When you say to your companion, 'Be quiet,' while the Imam is delivering the khutbah on Friday, you have indeed spoken uselessly (laghw)." - Sahih al-Bukhari 934, Sahih Muslim 851
And whoever comes, listens, and remains silent receives a great reward:
"Whoever performs wudū' well, then comes to the Friday prayer, listens and remains silent, will have his sins forgiven for what is between that Friday and the next, and for three more days." - Sahih Muslim 857