Sahih Bukhari Volume 1, Book 10, Hadith 704

حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، حَدَّثَنَا سُفْيَانُ، عَنْ إِسْمَاعِيلَ بْنِ أَبِي خَالِدٍ، عَنْ قَيْسِ بْنِ أَبِي حَازِمٍ، عَنْ أَبِي مَسْعُودٍ، قَالَ قَالَ رَجُلٌ يَا رَسُولَ اللَّهِ إِنِّي لأَتَأَخَّرُ عَنِ الصَّلاَةِ فِي الْفَجْرِ مِمَّا يُطِيلُ بِنَا فُلاَنٌ فِيهَا‏.‏ فَغَضِبَ رَسُولُ اللَّهِ صلى الله عليه وسلم مَا رَأَيْتُهُ غَضِبَ فِي مَوْضِعٍ كَانَ أَشَدَّ غَضَبًا مِنْهُ يَوْمَئِذٍ ثُمَّ قَالَ ‏"‏ يَا أَيُّهَا النَّاسُ إِنَّ مِنْكُمْ مُنَفِّرِينَ، فَمَنْ أَمَّ النَّاسَ فَلْيَتَجَوَّزْ، فَإِنَّ خَلْفَهُ الضَّعِيفَ وَالْكَبِيرَ وَذَا الْحَاجَةِ ‏"‏‏.

Narrated By Abu Mas'ud : A man came and said, "O Allah's Apostle! I keep away from the morning prayer because so-and-so (Imam) prolongs it too much." Allah's Apostle became furious and I had never seen him more furious than he was on that day. The Prophet said, "O people! Some of you make others dislike the prayer, so whoever becomes an Imam he should shorten the prayer, as behind him are the weak, the old and the needy."