Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"A man came to the Prophet (saw) and said: 'O Messenger of Allah! I stay behind and do not perform the morning prayer (in congregation) because of so-and-so, for he makes it too long for us.' I never saw the Messenger of Allah (saw) preaching with such anger as he did that day. He said; 'O people! There are among you those who repel others. Whoever among you leads others in prayer, let him keep it short, for among them are those who are weak and elderly, and those who have pressing needs.'" Sahih