Sahih Bukhari Volume 009, Book 089, Hadith Number 273.
Narrated By Abu Mas'ud Al-Ansari : A man came to Allah's Apostle and said, "O Allah's Apostle! By Allah, I fail to attend the morning congregational prayer because so-and-so (i.e., Muadh bin Jabal) prolongs the prayer when he leads us for it." I had never seen the Prophet more furious in giving advice than he was on that day. He then said, "O people! some of you make others dislike (good deeds, i.e. prayers etc). So whoever among you leads the people in prayer, he should shorten it because among them there are the old, the weak and the busy (needy having some jobs to do). (See Hadith No. 90, Vol. 1)