Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whenever a servant leads a people in prayer, he also takes on the responsibility for their prayer. If he performs it well, the reward is his; and if he falls short, (the reward of their prayer) is theirs and (the burden of the shortcoming) is upon him."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14978