Musnad Abu Ya'la al-Mawsili 49:9

Al-Hasan ibn Hammad al-Warraq narrated to us, Husayn al-Ju'fi narrated to us, from Za'idah, from Ibn Khuthaym al-Makki, from Nafi' ibn Sarjas, who said: I entered upon Abu Waqid al-Laythi in Makkah during the illness in which he died, and I heard him say—or he said to me—: "The Messenger of Allah (may Allah bless him and grant him peace) was the lightest of people in prayer, and the most constant of them upon himself."