Musnad Ahmad 1153:924

'Affan narrated to us, he said: Wuhayb narrated to us, he said: Musa ibn 'Uqbah narrated to us, he said: I heard Abu Salamah ibn 'Abd al-Rahman ibn 'Awf narrating from 'Aishah, the wife of the Prophet, may Allah bless him and grant him peace, that she used to say: The Messenger of Allah, may Allah bless him and grant him peace, said: "Follow the right course, draw near [to perfection], and receive glad tidings, for no one will enter Paradise by his deeds." They said: "Not even you, O Messenger of Allah?" He said: "Not even me, unless Allah, the Almighty and Majestic, covers me with mercy from Him. And know that the most beloved of deeds to Allah, the Almighty and Majestic, is that which is most constant, even if it is little."