Sayyiduna Abu Hurayrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "When one of you leads people in congregation, he should make it light, for among them are the weak, the old and the needy."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5266