Musnad Ahmad 1153:180

Abu Mu'awiyah narrated to us, Hisham ibn 'Urwah narrated to us, from his father, from 'Aishah, who said: A woman used to enter upon her and mention her diligence [in worship]. She said: So they mentioned that to the Prophet, peace and blessings of Allah be upon him, and he said: "Indeed, the most beloved of the religion to Allah, the Almighty and Majestic, is that which is persisted in, even if it is little."