Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "After me there will be rulers who will lead you in prayer. If they complete its bowing and prostration, then the reward is for both you and them; and if they fall short in it, then the reward is for you and the burden is upon them."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15026