Musnad Abu Ya'la al-Mawsili 117:170

Al-Hasan ibn al-Sabah al-Bazzar narrated to us, Mu'ammal ibn Isma'il narrated to us, from Sulayman ibn al-Mughirah, from Thabit, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) felt something [of pain/illness]. When morning came, it was said, "O Messenger of Allah, the effect of the pain is indeed clear upon you." He said, "I am as you see; I recited the seven long [surahs] last night."