Sahih Bukhari Volume 8, Book 73, Hadith Number 131.

Narated By Abu Mas’ud : A man came to the Prophet and said “I keep away from the morning prayer only because such and such person prolongs the prayer when he leads us in it. The narrator added: I had never seen Allah’s Apostle more furious in giving advice than he was on that day. He said, “O people! There are some among you who make others dislike good deeds) cause the others to have aversion (to congregational prayers). Beware! Whoever among you leads the people in prayer should not prolong it, because among them there are the sick, the old, and the needy.” (See Hadith No. 670, Vol 1)