Allah's Messenger said: "Whoever said: 'Be quiet' while the Imam is giving the Khutbah then he has committed Laghw (useless activity)."
Jami` at-Tirmidhi Book 4, Hadith 25
← Previous Hadith "Abu Sa'eed Al-Khudri entered (the mosque) on Friday while Marwan was giving the Khutbah, so he began praying. Two guards came to make him sit down but he refused until he had prayed. When he finished he came to us and we said: 'May Allah have mercy upon you. They nearly harmed you.' He said: 'I was not going to stop performing them (the two Rak'ah) after what I saw from Allah's Messenger.' Then he mentioned that a man who appeared untidy came on Fridy while the Prophet was delivering the Friday Khutbah, so he ordered him to pray two Rak'ah all the while the Prophet was delivering the Khutbah."

Jami` at-Tirmidhi Book 4, Hadith 24 Next Hadith → Allah's Messenger said: "Whoever steps over the necks of the people on Friday, he has taken a bridge to Hell."

Jami` at-Tirmidhi Book 4, Hadith 26