Musnad Abu Ya'la al-Mawsili 155:3

Abdullah ibn Umar ibn Aban narrated to us, Abd al-Rahim ibn Sulayman narrated to us, from Abu Ayyub al-Afriqi, from Safwan ibn Sulaym, from Sa'id ibn al-Musayyib, from Abu Hurayrah, from the Messenger of Allah (may Allah bless him and grant him peace), that he said: "There will come people, or there will be people, who will lead the prayer for you. If they complete it, it is for them and for you. And if they fall short, it is against them and for you."