(37) باب أَمْرِ الأَئِمَّةِ بِتَخْفِيفِ الصَّلاَةِ فِي تَمَامٍ
Abu Huraira reported:
The Apostle of Allah (ﷺ) said: When any one of you leads the people in prayer, he should be brief for among them are the young and the aged, the weak and the sick. But when one of you prays by himself, he may (prolong) as he likes.
Reference: Sahih Muslim 467 a
In-book reference: Book 4, Hadith 208
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 942