It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: When you lead the prayer as an imam, then lead a light (short) prayer, because among the worshippers are the elderly, the weak, and the sick. However, when one prays alone, he may prolong it as much as he wishes.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10522
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن، خ: 703، م:467