Musnad Abu Ya'la al-Mawsili 111:126

Narrated to us Zuhayr, narrated to us Muhammad, narrated to us Muhammad ibn ‘Amr, from Abu Umayyah, from Ibn ‘Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "I have been forbidden from praying behind those who are talking and those who are sleeping."