Sahih al-Bukhari Book 10, Hadith 98
Allah's Messenger (ﷺ) said, "If anyone of you leads the people in the prayer, he should shorten it for amongst
them are the weak, the sick and the old; and if anyone among your prays alone then he may prolong
(the prayer) as much as he wishes. "
A man came and said, "O Allah's Messenger (ﷺ)! By Allah, I keep away from the morning prayer only because So and so prolongs the prayer when he leads us in it." The narrator said, "I never saw Allah's Apostle more furious in giving advice than he was at that time. He then said, "Some of you make people dislike good deeds (the prayer). So whoever among you leads the people in prayer should shorten it because among them are the weak, the old and the needy."
A man came and said, "O Allah's Messenger (ﷺ)! I keep away from the morning prayer because so-and-so (Imam) prolongs it too much." Allah's Messenger (ﷺ) became furious and I had never seen him more furious than he was on that day. The Prophet (ﷺ) 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.''