Musnad Abu Ya'la al-Mawsili 108:35

Abu al-Rabi' narrated to us, Ya'qub narrated to us, 'Isa informed us, from Jabir ibn 'Abdullah, who said: The Messenger of Allah (may Allah bless him and grant him peace) prayed eight rak'ahs with us during the month of Ramadan and performed the witr prayer. When the following night came, we gathered in the mosque and hoped that he would come out to us, but we remained there until morning. Then we entered and said, "O Messenger of Allah, we gathered in the mosque and hoped that you would pray with us." He said, "I feared, or I disliked, that it would be made obligatory upon you."